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ISSN: Print -2349-0977, Online - 2349-4387


 
 Table of Contents  
PICTORIAL ESSAY: NEUROPATHOLOGY
Year : 2016  |  Volume : 2  |  Issue : 4  |  Page : 187-199

Spectrum of histopathology in spinal lesions


Department of Pathology, Institute of Human Behaviour and Allied Sciences, Delhi, India

Date of Web Publication22-Sep-2016

Correspondence Address:
Sujata Chaturvedi
Department of Pathology, Institute of Human Behaviour and Allied Sciences, Dilshad Garden, Delhi - 110 095
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2349-0977.191039

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  Abstract 

Spinal lesions are broadly categorized as lesions encountered in the spine and epidural space, lesions of spinal meninges, lesions of spinal nerve roots, and lesions of spinal cord. These are further sub classified into congenital malformations, inflammatory disorders, degenerative and reactive processes, cystic lesions, vascular malformations, and neoplasms. This pictorial essay highlights the histopathology of these lesions along with the clinical and radiology findings, where relevant.

Keywords: Extradural, extramedullary, intradural, intramedullary, s pine


How to cite this article:
Pant I, Chaturvedi S. Spectrum of histopathology in spinal lesions. Astrocyte 2016;2:187-99

How to cite this URL:
Pant I, Chaturvedi S. Spectrum of histopathology in spinal lesions. Astrocyte [serial online] 2016 [cited 2019 May 22];2:187-99. Available from: http://www.astrocyte.in/text.asp?2016/2/4/187/191039


  Introduction Top


The diversity of anatomic structures in the spinal region challenges both the clinicians and pathologists with a heterogeneous array of pathologic lesions. Spinal lesions pertain to tissues of the spine and epidural space which includes spine, meninges, spinal nerve roots and spinal cord. The nature of lesions can be classified into congenital malformations, inflammatory disorders, degenerative and reactive processes, cystic lesions, vascular malformations, and neoplasms [Box 1 [Additional file 1]],[Box 2 [Additional file 2]],[Box 3 [Additional file 3]],[Box 4 [Additional file 4]]. Considering the diversity of spinal lesions, an organized approach is preferable to minimize the diagnostic errors and make the histopathology report more clinically valuable. The first step of the diagnostic algorithm includes the analysis of the clinical and radiologic features because it narrows down the differential diagnosis to a significant extent. The next step includes the histopathology. The combination of clinical, radiological, and histopathological features forms the basis of the diagnostic approach toward a spinal lesion. The purpose of this article, which is based on the archival material from our department, is to make the reader aware of the findings of usual and unusual pathologies of the spinal lesions on histopathology along with the clinical and radiology findings, where relevant.


  Lesions of Spine and Epidural Space Top


Congenital malformations (meningocoele and meningomyelocoele)

A congenital malformation ranges from the innocuous spina bifida occulta to gross crippling deformities such as meningocoele and meningomyelocoele, where abnormal as well as exposed spinal cord tissue is elevated to or above the skin level.

A meningocoele is characterized by herniation of highly vascular arachnoid and dura mater through a vertebral defect with a covering of atrophic epidermis. It is most often lumbosacral. Although the cord remains within the spinal canal, it may show other anomalies such as hydromyelia, splitting, or tethering. Histopathology usually shows a thin and atrophic overlying epidermis. Islands of meningothelial cells are seen in the fibrotic dermis, which may form whorls and psammoma bodies [Figure 1]a.
Figure 1: (a) Histopathology showing fibrosed dermis (HE 100×), islands of meningothelial cells (inset HE 200×); (b) histopathology showing fibrotic meninges with interspersed clusters of adipose tissue (HE 100×).

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A meningomyelocoele is clinically identified by the translucent blue dome that transmits images of the enclosed spinal cord and nerve roots. The contents include abnormal spinal cord, nerve roots, dorsal root ganglia, meninges, blood vessels, and hyalinised connective tissue. Microscopically, the surface of the sac may be covered by squamous epithelium or fibrous tissue. The malformed tissue is predominantly formed of glia and neurons [Figure 2].
Figure 2: (a) Histopathology showing the sac (HE 200×); (b) malformed glial tissue (inset HE 200×).

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Inflammatory disorders

Spinal epidural tuberculosis is usually caused by the extension of tuberculous vertebral osteomyelitis into the epidural space. Clinically, there is a history of chronic backache and general malaise. Spinal cord compression (Pott's paraplegia) is a potential consequence often exacerbated by local vertebral collapse. Thoracic cord is most often involved. Macroscopically, there is usually extensive destruction, which may be associated with collapse of the affected vertebral bodies and intervertebral discs. The tuberculous exudate forms a tenacious grey membrane or a mass lesion that replaces epidural fat and is attached to the dura mater. Microscopically, the necrotic tissue shows the typical granulomatous inflammation with epithelioid cells, multinucleated giant cells, lymphocytes, caseous necrosis, and acid fast organisms [Figure 3]a and [Figure 3]b.
Figure 3: (a) Histopathology showing caseating epithelioid cell granulomas (HE 200×); (b) Langhans giant cell (HE 400×).

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Spinal epidural abscess may arise in continuity with a vertebral focus of the disease or as haematogenous deposit from an extravertebral site such as skin or the genitourinary tract. Epidural abscess typically manifest clinically with local tenderness and radicular or local pain, pyrexia, and neurologic deficits associated with nerve root or spinal cord compression. Thoracic region is most often affected. Staphylococcus aureus is the usual offending agent.[1] Macroscopically, purulent exudate is evident in the epidural space. Microscopy confirms the purulent material surrounded by inflamed granulation tissue [Figure 4].
Figure 4: Histopathology showing dense mixed inflammatory infiltrate (HE 400×).

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Other rare infections of the spine and epidural space include actinomycosis, aspergillosis, blastomycosis,  Brucellosis More Details, coccidioidomycosis, cryptococcosis, and echinococcosis.[2] Amyloid deposits, Langerhans cell histiocytosis, rheumatoid nodule, and sarcoidosis are additional inflammatory lesions of the spine.[3]

Degenerative and reactive processes

Herniated nucleus pulposus is the most common degenerative process encountered in the spine. A progressive series of structural and chemical alterations occurring in the intervertebral discs disturb the normal balance between the restraining property of the annulus fibrosus and the expulsive force of the nucleus pulposus, leading to the herniated nucleus pulposus through a defect in the annulus compressing the nerve roots or the spinal cord. Symptomatic lumbar disc herniation is the most frequent. Histologic changes show loss of lamellar architecture in the annulus, it develops fissures and acquires both chondrocytes and blood vessels while the nucleus shows fibrosis. Additional findings include prominent chondrocytes, areas of necrosis, and cystic degeneration. Although, generally the surgical specimen of herniated disc is labelled as “degenerative fibrocartilage” [Figure 5].
Figure 5: Histopathology showing degenerative fibrocartilage (HE 400×); prominent chondrocytes (inset HE 400×).

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Synovial cysts are small, discrete, often pain producing epidural masses related to joints between vertebral facet joints. These cysts are most commonly located in the lumbar region,[4] although rare cases have been reported in the thoracic and cervical region.[5] Histology shows largely fibrous wall containing cuboidal synovial cells lining the mucin containing cyst cavity [Figure 6].
Figure 6: Histopathology showing cyst wall lined by synovial cells (HE 400×); mucin containing cyst cavity (inset HE 400×).

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Calcifying pseudo neoplasm of the neuraxis is a fibrocalcific reactive lesion of unknown pathogenesis. In spine, it presents as an expansile extradural somewhat destructive mass that can occur in patients of all ages and at all spinal levels. Histologically, the tissue is largely amorphous with multinodular masses of fibrous connective tissue, peculiar granular debris, bone and calcification. Epithelioid cells at the periphery along with multinucleated cells may be seen in some lesions [Figure 7].
Figure 7: Histopathology showing fibrous connective tissue (HE 400×); epithelioid cells (inset HE 400×).

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Other degenerative and reactive processes include calcium pyrophosphate deposition, extramedullary hematopoiesis, fibrous dysplasia, gouty typhus, hydroxyapatite crystal deposition, Paget's disease, pigmented villonodularsynovitis, xanthoma, and xanthogranuloma.

Neoplasms and other tumors

Chordoma is a localized invasive and potentially metastasizing neoplasm derived from notochordal remnants. Approximately 80% of the chordomas arise in the sacrum or the clivus. Cervical, thoracic, and lumbar segments are rarely affected. Clinically, pain is the predominant symptom. Anterior extension of sacral lesions adds rectal discomfort and dysfunction. Microscopically, it shows the neoplastic cells arranged in lobules of variable size separated by fibrous septae. Tumor cells differ considerably in appearance; some have well-defined homogeneous eosinophilic cytoplasm arranged in sheets, clusters, cords, and strands. Most chordomas have a spectrum of cells exhibiting varying amounts of mucin. Large cells markedly engorged with mucus vacuoles (physaliphorous cells) are the hallmark of chordoma [Figure 8]. Immunoreactivity for cytokeratins, epithelial membrane antigen, (EMA) is present in the cells of a chordoma.
Figure 8: (a) Histopathology showing lobules of neoplastic cells (HE 200×), (b) physaliphorous cells (HE 400×); (c) tumor cells strongly immunopositive for CK (400×); (d) tumor cells strongly immunopositive for EMA (400×).

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Vertebral hemangioma in the spine is an aggregate of thin-walled vessels. Vertebral hemangiomas are usually discovered incidentally. Symptomatic cases present with local pain and tenderness or with signs of nerve root or spinal cord compression. Histopathology shows delicate serpiginous vascular channels [Figure 9].
Figure 9: Histopathology showing delicate serpiginous vessels (HE 400×); vessels against the fibrous stroma (inset HE 400×).

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Lipoma and angiolipoma are commonly encountered in the spinal epidural space. Most occur at the midthoracic level and affect women. Histopathology shows clusters of mature adipocytes separated by thin fibrous septae [Figure 10]a; Angiolipoma shows blood vessels in addition to the clusters of these mature adipocytes [Figure 10]b.
Figure 10: (a) Histopathology showing lobules of mature adipose tissue (HE 100×).(b) Histopathology showing lobules of mature adipose tissue with interspersed blood vessels (HE 200×).

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Epidural lipomatosis as a focal form of expansion of adipose tissue is a well-known but uncommon response to elevated levels of endogenous steroids as in Cushing's syndrome or exogenous glucocorticoids. Idiopathic expansion of epidural adipose tissue is rare.

Lymphoma and leukemia are frequently encountered in the spinal vertebrae and the epidural space. Although the leukemic infiltrates may compress the spinal cord producing functional deficits, lymphomatous involvement occurs with higher frequency. Adults are affected commonly and midthoracic segment is involved in most of the cases. Clinically, signs and symptoms of spinal cord compression may be the initial presenting manifestation of the disease [6] but they are more often late events in the course of systemic lymphoma. All variants of lymphoma and leukemia may be encountered at these locations. Histopathology shows proliferation of discohesive diffusely infiltrating atypical lymphoid cells [Figure 11]a, often arranged in an angiocentric pattern. Vast majority of tumors are B cell lymphomas (CD 20+) [Figure 11]b.
Figure 11: (a) Histopathology showing atypical lymphoid cells (HE 400×), (b) tumor cells strongly immunopositive for CD45 (400×).

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Metastatic carcinoma of the spine and epidural space usually presents with acute spinal cord symptoms. Pain is usually the initial symptom, thoracic spine being the most commonly involved. The disease usually is recognized radiologically. Epidural infiltration usually follows lytic vertebral involvement that predisposes to pathologic fractures. Common primary sites include the lung, breast, and prostate.[7] Hosting bone shows a wide spectrum of reactions varying from minimally affected trabeculae to totally destroyed trabeculae. Microscopically, the lesions are identified by the epithelial nature of the metastatic carcinomas [Figure 12]a and [Figure 12]b.
Figure 12: (a) Histopathology showing malignant epithelial cells (HE 100×), malignant squamous epithelial cells (inset HE 200×); (b) tumor cells strongly immunopositive for CK (200×).

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Multiple myeloma and plasmacytoma frequently affects the spine and the epidural space. The incidence is maximal during the fifth to seventh decades, with preferential involvement of the thoracic segment. Neoplastic foci of these plasma cell neoplasia exhibit masses with typical grayish purple hue and a fleshy consistency. Histopathology of these tumors show neoplastic plasma cells exhibiting the eccentric nuclei with clock-face chromatin and cytoplasmic basophilia [Figure 13]. Binucleation may be present. Diagnosis of solitary plasmacytoma should be rendered only after a thorough negative hematologic evaluation. Initially, it has to be a tentative diagnosis until confirmed by long-term follow up.
Figure 13: Histopathology showing neoplastic plasma cells (HE 400×); eccentric nuclei showing typical cartwheel appearance (HE 400×).

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Neuroblastic and neuronal neoplasms usually in children appear as either primary lesions of the epidural space or secondary extensions of a paravertebral primary. Rare examples are hematogenous metastasis. As fleshy, lobulated, and discrete masses, the lesions impinge upon the spinal cord and its nerve roots, producing signs and symptoms of cord compression as well as local or radicular pain. Microscopically, spinal neuroblastomas exhibit the neuroblasts, focal fibrillary background, patchy necrosis, and calcification [Figure 14]. Associated ganglion cells renders the diagnosis of ganglioneuroblastomas, and associated schwann cells renders the diagnosis of ganglioneuromas.
Figure 14: (a) Histopathology showing malignant round cells (HE 200×); (b) perivascular pseudorosettes (HE200×); (c) pleomorphic tumor cells (HE 400×);(d) brisk mitosis (arrow) (HE 400×).

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Sacrococcygeal teratoma is a usually well-differentiated germ cell neoplasm of the sacrum. Most of these sacrococcygeal teratomas are obvious during the neonatal period as a caudal deformity that can reach enormous proportions. Uncommonly, they appear later in children and adults when pain and mechanical interferences with bowel, bladder, and sciatic nerve function herald their presence. These are more frequent in females. Most originate in the coccygeal and presacral regions, from which they surface in the posterior midline or protrude laterally into a buttock. Surgical specimen consists of solid and cystic tissue. Cysts vary in size with their contents ranging from watery to mucinous or keratinous to sebaceous. Hairs are present intermingled with the sebaceous material. Solid regions may show calcified areas. Microscopically, sacrococcygeal teratoma shows derivatives of all three germ layers comprising ectodermal, mesodermal, and endodermal components distributed in a pattern-less array [Figure 15].
Figure 15: (a) Histopathology showing fluid filled cavities (HE 100×); (b) adipose tissue lobules (HE 200×); (c) lymphoid tissue (HE 200×); (d) nerve fascicles (HE 200×); (e) skeletal muscle bundles (HE 200×);(f) epithelial cell clusters (HE 400×).

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Sacral ependymoma occasionally occurs primarily in the sacrum or parasacral soft tissues, without an associated intradural mass. Histopathology of sacral ependymoma typically shows features of myxopapillary ependymoma showing more epithelial appearance [Figure 16]. Ectopic ependymal tissue in the scarum and the congenital ependymal cell rests are the source of these sacral ependymomas.
Figure 16: (a) Histopathology showing a moderately cellular ependymal tumor (HE 100×); (b) ependymal cells showing salt and pepper chromatin (HE 200×); (c) perivascular pseudorosettes (HE 200×); (d) GFAP immunoreactivity (200×); (e, f) histopathology showing myxopapillary ependymoma (HE 400×).

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Miscellaneous neoplasms and non-neoplastic tumors of the spine and epidural space include epidural amyloidoma, aneurysmal bone cyst, arteriovenous malformation, carcinoid tumor, chondroblastoma, chondroma, chondromyxoid fibroma, chondrosarcoma, mesenchymal chondrosarcoma, epithelioid hemangioendothelioma, peripheral primitive neuroecrodermaltumor or Ewing's sarcoma, fibromatosis, and giant cell tumor.


  Lesions of Spinal Meninges Top


Neoplasms

Meningiomas constitute 25–35% of all primary Intraspinal tumors. Etiology of spinal meningiomas is unknown, aside from the rare examples that appear to be radiation induced [8] or those that arise in individuals with neurofibromatosis type 2 (NF2). Clinically, spinal meningiomas manifest after the fourth decade with a predilection for females exhibiting a Male: Female ratio of 1:4.[9] Spinal meningiomas frequently occur in the thoracic region, cervical region is affected less often, lumbar region is rarely affected, and sacral region is never affected. Most meningiomas remain within the intradural space, although a few penetrate the duramater to reach the adipose tissue of the epidural compartment. Infiltration into the regional soft tissue and bone is rare.[10] Meningiomas arising primarily in the epidural compartment and skin are quite rare.[11] Intramedullary spinal meningiomas are extremely rare.[12]

Radiology shows the mass with classical dural base, contrast enhancement, and dural tails. Microscopically, meningiomas show the typical meningothelial cells arranged in whorls and fascicles [Figure 17]. However, highly calcified psammomatous variant is more frequent in the spinal region. Differential diagnoses of spinal meningiomas include schwannomas and solitary fibrous tumor encountered in the spinal canal.
Figure 17: Histopathology showing neoplastic meningothelial cells forming whorls (HE 200×).

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Hemangiopericytomas are less common in the spine than their intracranial counterparts. Onset is during adulthood, commonly located at the intradural-extramedullary position. Grossly, these are circumscribed, lobulated masses. Histopathology shows a highly cellular tumor with characteristic dilated staghorn type vessels, rich network of reticulin fibres and diffuse immunoreactivity for CD 34 in the tumor cells [Figure 18]a,[Figure 18]b,[Figure 18]c. Spinal hemangiopericytomas are locally aggressive, show frequent recurrences, and have a tendency for late distant metastasis.
Figure 18: (a) Histopathology showing a highly cellular tumor with the staghorn sinusoids (HE 100×); (b) stromal cells (HE 200×); (c) rich network of reticulin fibres (reticulin 200×).

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Melanocytic neoplasms are rare intraspinal neoplasms derived from meningeal melanocytes, range from low grade melanocytomas, through difficult to grade transitional forms to malignant melanomas.[13] Histopathology of melanocytomas varies from a prominent nested pattern to patternless sheets to fascicular pattern. In malignant melanoma, the histologic pattern is more likely to be sheet-like or fascicular. Nuclear atypia is the rule with prominent nucleoli. Mitosis is brisk. These neoplasms are immunopositive for melanocyte markers such as HMB45 and melan A [Figure 19].
Figure 19: (a) Histopathology showing the lobular arrangement of the tumor (HE 100×); (b) melanoma cells (HE 200×); (c) prominent eosinophilic nucleoli (HE 200×); (d) GFAP immunoreactivity (GFAP 200×).

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Tumors of adipose tissue include neoplastic or malformative masses of mature adipose tissue although lipomatous masses are an infrequent cause of spinal cord and nerve root compression. Lipomas may affect patients of all ages and are encountered throughout the intradural space, however, isolated lipomas favor the cervical and upper thoracic regions. In the lower spinal canal, lipomas are mostly malformative in nature, and are generally associated with spina bifida, meningocoele, dermal sinus, lipomeningocoele, or leptomyelolipoma. Macroscopic appearance is of bright-yellow lesions adherent to the spinal cord. Microscopically, these masses show clusters of mature adipose tissue with skeletal or smooth muscle, neuroglia, and fibrous tissue in varying proportion asassociated findings [Figure 1]b.

Other rare primary meningeal tumors include mesenchymal chondrosarcoma, solitary fibrous tumor, leiomyosracoma, and meningeal gliomatosis. Metastatic carcinoma and lymphoma in the leptomeninges are attributed to the free flow of cerebrospinal fluid within the craniospinal subarachnoid space. Metastases in the leptomeninges are frequently from the lung, stomach, or breast carcinomas [Figure 12].Seeding of primary intracranial neoplasms in the spinal meninges is most commonly seen in the medulloblastoma, primitive neuroectodermaltumors (PNETs), germ cell tumors and high grade gliomas.[13]

Cystic lesions

Epidural meningeal cyst is most often situated in the posterior midline. Microscopically, it is bilayered and consists of a thick duramater-like layer of collagen and an inner less constant membrane of arachnoidmater [Figure 20]a. Arachnoid cyst of the spine usually presents as multiple lesions. Origin of these cysts is attributed to trauma, hemorrhage, inflammation, or genetic influences. Histopathology shows delicate connective tissue with a covering of meningothelial cells [Figure 20]b.Ependymal cysts are commonly located in the intradural space. Histologically, these cysts are composed of simple cuboidal to columnar ciliated epithelium [Figure 20]c.
Figure 20: (a) Histopathology showing the cyst wall formed by collagen and arachnoidal cells (HE 200×);(b) cyst wall lined by meningothelial cells (HE 400×); (c) cyst wall lined by cuboidal and columnar cells (HE 400×).

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Epidermoid and dermoid cysts are most frequent in the lumbosacral region. Mostly, these are extramedullary, however, rare examples are entirely intramedullary. [14] Few case reports in the literature show epidermoid and dermoid cysts partly embedded within the spinal cord.[15] Macroscopically, these are glistening white or cream-colored cystic lesions reflecting their contents of either flaky keratin or greasy sebaceous material. Histopathology shows a lining of keratinizing squamous epithelium in both lesions, however, the wall of dermoid cysts contains sebaceous glands and hair follicles [Figure 21]a and [Figure 21]b.
Figure 21: (a) Histopathology showing the cystic cavity filled with lamellated keratin (HE 200×);(b) cyst wall showing hair follicle (HE 200×).

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Neurenteric and bronchogenic cysts are uncommon intradural cysts presumably arise from the displaced remnants of the developing gastrointestinal tract and from the respiratory system. Macroscopically, these are opalescent smooth surfaced mass. Microscopically, these cysts are lined by a well-differentiated columnar epithelium with or without cilia and mucus globules [Figure 22]a.
Figure 22: (a) Histopathology showing the cyst wall lined by columnar epithelium (HE 400×); (b) cyst wall showing collagenous tissue (HE 200×) and nerve fascicles (inset HE 200×).

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Perineurial (Tarlov) cysts are most frequent in the sacral region and are usually bilateral. These cysts presumably arise through degenerative changes that create a cleavage between the epineurium and perineurium of exiting nerve roots or dorsal root ganglion.[16] Microscopically, these cysts show collagenous tissue and nerve fascicles [Figure 22]b.

Inflammatory lesions

Sarcoidosis in the spinal meninges occurs as a mass clinically or as a diffuse contrast enhancing leptomeningeal mass on radiology. Histopathology shows discrete non caseating granulomas typical of sarcoidosis [Figure 23]a.Hypertrophic pachymeningitis denotes fibrous thickening of the duramater associated with a chronic inflammatory infiltrate. Clinically, it presents with pain when nerve roots are involved and with sensorimotor deficits when there is impingement upon the spinal cord. Cervical region is mostly affected. Microscopically, it shows dense fibrous tissue with chronic inflammatory infiltrate [Figure 23]b.Arachnoid plaques are usually the common incidental postmortem findings within the arachnoid membrane of the thoracolumbar spinal cord. Only rarely these plaques are symptomatic.[17] Microscopically, these lesions are sufficiently lamellated resembling bone, but are rarely calcified.
Figure 23: (a) Histopathology showing noncaseating granulomas (HE 400×); (b) fibrous tissue with inflammatory infiltrate (HE 400×).

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  Lesions of Spinal Nerve Roots Top


Primary neoplasms

Schwannoma and melanocytic schwannoma of the spinal nerve roots are the neoplasms derived from the nerve sheath. Schwannomas may originate from nerve roots at all spinal levels from the cervicomedullary junction to the cauda equina. The peak incidence is during the fifth and sixth decades. Clinically, it presents with radiating pain and weakness. Many of the multiple nerve root schwannoma in patients with NF2 are asymptomatic for long periods.[18] Radiology shows the characteristic dumbbell or hourglass shaped mass. Although schwannomas may burrow into the cord, rarely, are they entirely intramedullary. Microscopically, spinal schwannomas show the classical picture exhibiting areas of compact elongated cells with nuclear palisades and less cellular loosely textured cells with indistinct processes and variable lipidization [Figure 24]a. Verocay bodies are more common in spinal schwannomas [Figure 24], inset]. Melanotic schwannomas mostly show spindle cells, but epithelioid forms are occasionally seen. Melanin is present within the tumor cells, in the stroma or aggregated in melanophages, showing strong immunopositivity for HMB45 and S100. Uniform pericellular reticulin staining favors the diagnosis of schwannoma and also differentiates it from melanocytoma.
Figure 24: (a) Histopathology showing a biphasic tumor (HE 400×) with characteristic nuclear palisades (inset HE 200×);(b) wavy Schwann cells (HE 200×), cell morphology (inset HE 400×).

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Neurofibroma of the spinal nerve roots is mostly associated with NF1.[19] Usually, these are asymptomatic although often multiple in number. Cervical region is usually affected. Macroscopically, the tumor has a translucent glistening appearance. Microscopically, the tumor shows a chaotic array of wavy Schwann cells bundled or dispersed in a collagenous matrix [Figure 24]b.

Other rare primary neoplasms of spinal nerve roots include paragangliomas, ependymomas, and hemangioblastomas.

Secondary neoplasms (carcinoma, leukemia, and lymphoma)

As spinal nerve roots traverse the subarachnoid space, they are bathed in cerebrospinal fluid and are exposed to the floating tumor cells, which get attached to these nerve roots conveniently. Predominantly, epithelial and hematopoietic neoplasms show such leptomeningeal dissemination.


  Lesions of Spinal Cord Top


Congenital malformations

Congenital malformations of the spinal cord may be categorized as the evident external dysraphisms and the internal changes accompanying spina bifida occulta. The dysraphisms include meningomyelocoele and diastematomyelia while anomalies associated with spina bifida occulta include lipomeningocoele and tethered cord. Microscopically, in meningomyelocoele, the surface of the sac may be covered by squamous epithelium or fibrous tissue. The malformed tissue is predominantly formed of glia and neurons [Figure 2]. Diastematomyelia can be subclassified into two types. Type I diastematomyelia consists of two hemicords, each contained within its own dural tube and separated by a rigid osseocartilaginous midline septum. Type II consists of two hemicords housed in a single dural tube separated by a non rigid, fibrous median septum.[20] Diastematomyelia is usually diagnosed by ultrasound or magnetic resonance imaging (MRI).[21] Diastematomyelia may occur in isolation, or may be associated with spinal abnormalities, such as myelomeningocele, meningocele, spinal lipoma, neuroenteric cysts, or dermal sinus, as well as congenital defects of the spine, including hemivertebrae, butterfly vertebrae, and scoliosis.[22] Histopathology of lipomeningocoele shows clusters of mature adipocytes in addition to the fibrotic meninges [Figure 1]b. Microscopically, tethered cord shows a complex cellular arrangement with sheets of meningothelial proliferation, bone, fat tissue, and fibrosis.

Inflammatory disorders

Demyelinating disease and transverse myelopathy are the common inflammatory disorders of the spinal cord. Demyelinating disease is identified by the principal hallmark of the presence of the macrophages.[23] Immunohistochemical markers such as HAM-56 and KP-1 are helpful. Transverse myelopathy does not have any pathognomonic abnormalities on histopathology. Macrophages and sometimes a chronic inflammatory infiltrate are typical features. Distinction between demyelinating disease and transverse myelopathy cannot always be drawn due to the overlapping histopathological findings.

Other inflammatory disorders of the spinal cord parenchyma include pyogenic abscess, tuberculosis, brucellosis, coccidioidomycosis, cryptococcosis, cysticercosis, echinococcosis, schistosomiasis, granulomatous angiitis, toxoplasmosis, Langerhans cell histiocytosis,  Rosai-Dorfman Disease More Details, and paraneoplastic disease.

Vascular malformations

Cavernous angioma of the spinal cord is a vascular malformation made up of closely opposed vessels forming a dark botryoid mass. Microscopically, the mass shows hyalinized, often thrombosed, and sometimes recanalized vessels forming compact conglomerates or lying scattered in the gliotic cord parenchyma [Figure 25]a. Arteriovenous malformation of the spinal cord consists of large serpentine vessels that forms projections coiled around the cord and the exiting nerve roots. Most vessels lie on the dorsal surface of the cord and consist largely of veins, some of them arterialized. Smaller numbers of hyalinised vessels lie within cord parenchyma. Symptoms are attributed to pressure, ischemia, or rarely hemorrhage. Microscopically, AV malformation of the spinal cord shows abnormally large vessels with variable proportions of smooth muscle and fibrous tissue [Figure 25]b.
Figure 25: (a) Histopathology showing the conglomerates of vessels (HE 100×); (b) abnormal vasculature with fibrous tissue (HE 100×).

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Neoplasms

Astrocytic neoplasms of the spinal cord may be divided into two clinicopathologically distinct groups: Diffuse or diffusely infiltrative astrocytoma and the better circumscribed pilocytic astrocytoma. This distinction is important because the two tumor types differ in their growth pattern, biologic behaviour, optimal therapy, and prognosis.

Diffuse infiltrative astrocytomas range from WHO grade II to IV. These are uncommon neoplasms affecting both children and adults. Clinical features include pain, motor deficits, sensory disturbances, and abnormalities of sphincter function. An insidious onset with gradual progression characterizes the better differentiated lesions whereas a more acute onset typifies anaplastic lesions such as glioblastoma. Diffuse astrocytomas on MRI show nonenhancing widening of the spinal cord whereas glioblastomas in the spinal cord are usually contrast enhancing. Microscopically, WHO grade II astrocytomas show a tumor composed of atypical fibrillary or gemistocytic astrocytes [Figure 26]a. As anaplasia appears, the cells become increasingly pleomorphic and densely packed. Anaplastic (WHO grade III) astrocytomas reveal atypia along with brisk mitosis [Figure 26]b. In addition to mitosis, microvascular proliferation and necrosis are the characteristic histopathological features of glioblastoma (WHO grade IV) [Figure 27]c and [Figure 27]d.
Figure 26: (a) Histopathology showing neoplastic fibrillary astrocytes (HE 200×); (b) markedly pleomorphic astrocytes (HE 400×); (c) anaplastic astrocytes (HE 400×); (d) large areas of necrosis (HE 200×) and microvascular proliferation (inset HE 400×).

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Figure 27: (a) Histopathology showing a biphasic tumor (HE 100×); (b) abundant piloid cells (HE 200×); (c) Rosenthal fibres (arrow HE 400×); (d) eosinophilic globular bodies (arrow HE 400×).

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Pilocytic astrocytoma of the spinal cord usually affects both children and adults with presenting signs and symptoms of weakness, sensory deficits, and pain. Frequently pilocytic astrocytomas of the spinal cord are cyst-associated and contrast enhancing mass. Microscopically, it shows a biphasic pattern; loose glial tissue having extensive cystic changes intermingled with compact piloid tissue. The loose glial tissue may show microcysts and vacuoles whereas the compact areas exhibit islands or sheets of compact elongated cells that are markedly fibrillated and often contain prominent Rosenthal fibres. The nuclei of these cells are benign in appearance [Figure 27]. Hyperchromasia and degenerative atypia are common in long standing tumors.

Ependymomas of the spinal cord are the most common gliomas of the spinal cord and are divided into the classical cellular ependymoma and the myxopapillary ependymoma. Myxopapillary ependymoma is restricted to the conus medullaris and filum terminale. The incidence of cellular ependymoma peaks during the fourth and fifth decades. Most spinal cord ependymomas are intramedullary but occasional examples, although intradural, arise outside the spinal cord.[24] Microscopically, cellular ependymomas consist of cellular sheets interrupted by perivascular anuclear zones or pseudorosettes [Figure 16]a. True rosettes or canals are less frequent histological features. Myxopapillary ependymomas usually occur in adults and rarely in children. Signs and symptoms include either sphincter disturbances or deficits related to compression or involvement of the conus medullaris or sacral nerve roots. Abundant mucin that characterizes this lesion can be visualized radiologically as hyperintensity or whiteness on nonenhanced T1-weighted MRI. Histopathology shows variable architecture ranging from papillary, epithelial, or fibrillary. Characteristically mucin is abundant and often located within the walls of the vessels and less commonly as a diffuse deposition [Figure 16]b.

Oligodendroglioma and ganglion cell tumors are extremely rare entities in the spinal cord. Microscopically oligodendroglioma shows uniformly round nuclei, bland chromatin with sharply defined nuclear membranes, clear perinuclear haloes imparting a “fried-egg” or honeycomb appearance and a rich chicken-wire like branching capillary network [Figure 28]. Ganglion cell tumors are identified by the well-differentiated ganglion cells.
Figure 28: Histopathology showing the typical honeycomb appearance (HE 200×) and the chicken wire network (inset HE 400×).

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Hemangioblastomas of the spinal cord occur primarily in adults with a peak incidence during third to fifth decades, preferentially affect men,[25] and show an occasional association with additional features of von Hippel–Lindau disease.[26] Spinal hemangioblastomas are discrete, highly vascular, and lipid-rich tumors. Depending on the degree of lipidization, the tumors have a distinctive red-yellow variegation apparent on cut sections. Microscopically, these tumors show two main components: Vascular elements and interstitial or stromal cells [Figure 29]a. The varied ratio of these two elements, the calibre of the vascular channels and the degree of lipidization of stromal cells contribute to the histologic heterogeneity of hemangioblastomas [Figure 29]b and [Figure 29]c. Dense reticulin circumscribes nests of stromal cells.
Figure 29: (a) Histopathology showing the typical vascular and stromal element (HE 100×); (b) vessels of varying calibre (HE 200×); (c) vacuolated stromal cells (HE 400×).

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Paragangliomas are uncommon neuroendocrine neoplasms in the cauda equina region. Most occur in adults. Delicately encapsulated, soft, and vascular, these neoplasms usually arise from the filum terminale, and less often from a nerve root.[27] Histologically, most paragangliomas display the characteristic Zellballen architecture [Figure 30] made up of lobules of paraganglioma (chief) cells. These tumor cells have the distinctive nuclei with a “salt-and-pepper” chromatin [Figure 30]. S-100 positive sustentacular cells surround lobules of chief cells. In addition, neuroendocrine or carcinoid tumor-like patterns are commonly present. Ganglion cells occur in close to 50% of lesions.[27]
Figure 30: (a) Histopathology showing thetumor with typical Zellballen architecture (HE 200×); (b) tumor cells showing strong immunopositivity for NSE (NSE 400×).

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Intramedullary schwannoma of the spinal cord usually arises from the small perivascular bundles of peripheral nerves present within the spinal cord. Histopathology shows the classical picture exhibiting areas of compact elongated cells with nuclear palisades and less cellular loosely textured cells with indistinct processes and variable lipidization. Verocay bodies are the associated findings [Figure 24]a. Rare examples are melanotic.[28]

Metastatic neoplasms of the spinal cord are quite uncommon; however, they may appear in biopsy material, usually in the setting of a known, already metastasizing cancer. Lung is the most common source. Other intramedullary neoplasms of the spinal cord include germinoma, atypical teratoid rhabdoid tumor, hamartoma, lipoma, lymphomatoid granulomatosis, meningioma, neurocytoma, pleomorphic xanthoastrocytoma, primary CNS lymphoma, primitive neuroectodermal tumor, and teratoma.


  Conclusion Top


Our experience shows that location based approach combined with specific clinical and imaging finding is helpful in offering a clinically relevant histopathology report. It is expected that this pictorial essay of histopathological spectrum of spinal lesions would be of help to neuroscience units dealing with spinal lesions.

Acknowledgements

The authors acknowledge the help of Mr Prashant Shende (Laboratory technician), Ms Meetu Raj Behal (Laboratory technician), and Ms Kavita Dhaiya (Laboratory assistant) for their untiring technical support.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23], [Figure 24], [Figure 25], [Figure 26], [Figure 27], [Figure 28], [Figure 29], [Figure 30]



 

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