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| LETTER TO THE EDITOR |
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| Year : 2014 | Volume
: 1
| Issue : 2 | Page : 162-165 |
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Primary endobronchial synovial sarcoma
Ashwani Tandon1, Shantveer G Uppin1, Sujata Patnaik2, C Sundaram1
1 Department of Pathology, Nizam's Institute of Medical Sciences, Punjagutta, Hyderabad, India
2 Department of Radiology, Nizam's Institute of Medical Sciences, Punjagutta, Hyderabad, India
| Date of Web Publication | 31-Jul-2014 |
Correspondence Address:
Dr. Ashwani Tandon
Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad - 500 082
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/2349-0977.137867
How to cite this article:
Tandon A, Uppin SG, Patnaik S, Sundaram C. Primary endobronchial synovial sarcoma. Astrocyte 2014;1:162-5 |
Sir,
Metastatic sarcomas are more common than primary pulmonary sarcomas. [1],[2] Synovial sarcoma (SS) is characterized by chromosomal translocation, t(X; 18) (p11.2; q11.2) in extremities. [3] Primary pulmonary SS is very rare compared with metastatic sarcoma, accounting for less than 0.5%. [4] It shares similar histomorphological and chromosomal translocations as its soft-tissue counterpart. [4],[5],[6],[7],[8] It offers a diagnostic challenge, and is often misdiagnosed as either a primary pulmonary spindle cell sarcoma/carcinoma or metastatic sarcoma. [4],[5],[6],[7] Although immunohistochemistry (IHC) is a useful adjunct, it lacks specificity. Hence the utility of fluorescent in situ hybridization (FISH) techniques to detect specific chromosomal translocation for diagnosing SS, especially in unusual locations like the lung. [4],[5] Herein, we present a case of primary pulmonary SS presenting as endobronchial mass, the diagnosis of which was confirmed by FISH study with SS18 break-apart probe.
A 45-year-old female patient presented with history of cough and hemoptysis for 6 months. Chest X-ray revealed a large lobulated mass lesion in the right lower lobe [Figure 1]a]. Computed tomography (CT) scan of the chest confirmed the lobulated mass lesion in superior segment of right lower lobe; the mass exhibits inhomogenous enhancement [Figure 1]b]; on lung window, the mass lesion is marked by a large area of consolidation; the mass has either infiltrated into the surrounding alveolar space or has also resulted in secondary consolidation [Figure 1]c]. Bronchoscopy revealed an endobronchial mass lesion in the right lower bronchus. Bronchial biopsy and bronchoalveolar lavage were inconclusive. She underwent right lower lobectomy and postoperative period was uneventful. Gross specimen of right lower lobectomy was externally unremarkable with shiny pleura. Cut section revealed gray-white, soft friable tumor filling bronchus of right lower lobe and measuring 2.5 × 2 cm noncapsulated with partial circumscription. Microscopically, a infiltrative tumor was noted with predominant intrabronchial location [Figure 2]a]. The tumor cells were arranged in either solid sheets or short fascicles in a collagenous stroma. Focal hemangiopericytomatous pattern were noted. Tumor was comprised of closely packed, uniform-appearing ovoid to plump spindly cells, with scant cytoplasm and indistinct cell borders [Figure 2]b]. At places tumor was infiltrating in alveolar space. No epithelial component was identified. Mitosis was occasional (1-2/50 high power field). Foci of hemorrhage, necrosis, and lymphomononuclear inflammatory infiltrate were noted [Figure 2]a-e]. IHC and molecular studies were performed to confirm the diagnosis. | Figure 1 a, b, c: Chest X-ray and CT thorax depict a lobulated mass in superior segment of the right lower lobe, diagnosed as primary endobronchial synovial sarcoma by the pathologist.
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 | Figure 2: Whole mount view show tiny endobronchial tumor (a); (b and c) Spindle cell tumor with endobronchial lining (10× and 40×); (d)Tumor with lung parenchymal Infiltration (10×); (e and f) Higher magnification of spindle cell tumor with hemangiopericytomatous pattern (20×); Immunohistochemistry with BCL2, (g) EMA (h) and Vimentin (i) Positivity in tumor cells; Florescent in situ hybridization signal first and second encircled tumor nuclei show single fusion and two break apart signals while third normal nuclei show two fusion signals (j and k).
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Immunohistochemical stains were performed using polymer-based technique (Biogenex). The primary antibodies used were pan-cytokeratin, vimentin, EMA, BCL-2, S-100, SMA, TTF-1, and chromogranin. The tumor cells showed strong immunoreactivity to vimentin, BCL-2 [Figure 2]c and d] and focal reactivity to EMA. IHC for SMA, CK, chromogranin, and TTF-1 was negative [Figure 2]g-i]. FISH was performed on the paraffin tissue using LSI SYT dual color break-apart rearrangement SS18 probe (Vysis). Sections were deparaffinized in xylene and dehydrated. Sections were pretreated using paraffin pretreatment reagent kit II (Vysis) and followed by protease solution at 37°C washing and dehydrating for 1 min in increasing concentrations of alcohol after which they were air-dried. Ten microliters of probe mixture were applied to the slides, overlaid with a coverslip, which was sealed with rubber cement. Slides were denatured for 5 min at 73°C and hybridized for at least 16 h at 37°C in a ThermoBrite™ hybridizer. Following hybridization, the slides were washed SCC/0.3%NP40 at appropriate temperature, counterstained with DAPI II (Abbott MolecularInc.) and coverslip was applied. The slide was analyzed under a fluorescent microscope (Zeiss AXIOScope, Germany) equipped with Isis software (Metasystem). Fifty nonoverlapping nuclei, which were clearly identified and contained unequivocal signals, were counted. A probe was considered to be split when the orange and green signals were separated by a distance greater than the size of one hybridization signal. Case show break apart signals in 35% nuclei and interpreted as positive. FISH confirmed the diagnosis of SS [Figure 2]j-k].
SS is an aggressive neoplasm, accounting for up to 5-10% of soft-tissue sarcomas. [3] Increasing numbers of reports of primary pulmonary SS are being published mainly due to the use of molecular techniques and FISH. [4],[5]
The present case is of primary pulmonary SS presenting as an endobronchial growth. Three studies had described such an event previously in the literature. [7],[8],[9] Although, the exact histogenesis of primary pulmonary SS is uncertain and may origin in pleuripotent mesenchymal cells of bronchial submucosal stromal tissue. [9]
Morphologically these neoplasm are similar with its soft-tissue counterpart. [3],[4],[5],[6],[7],[9] Among several histological variants of SS, monophasic fibrous subtype is difficult to diagnose and needs to be distinguished from sarcomatoid carcinoma, sarcomatoid variant of mesothelioma, fibrosarcoma, leiomyosarcoma, Ewing's sarcoma, spindle cell thymoma, and solitary fibrous tumor (SFT) as well as metastatic sarcomas. [4],[5],[6],[9] In the present case, differential diagnosis of spindle cell carcinoid was also considered in view of endobronchial location. The IHC results helped in excluding these possibilities. The biphasic subtype is easily identifiable. [9] Metastatic SS to the lung was excluded with a thorough clinical and radiological examination to exclude primary elsewhere. Ancillary techniques like IHC and molecular studies have definite role in accurate diagnosis. In our case, the tumor demonstrated strong and diffuse positivity for vimentin, BCL-2, and focal positivity for EMA. This case was negative for CK and CD99 by IHC and make diagnosis more challenging by IHC. BCL-2 expression is nonspecific and can be observed in SFT. Hence, IHC markers cannot be reliably used to discriminate SS. [6],[7],[8]
SSs are characterized by the specific chromosomal translocation t(X;18) (p11.2;q11.2), which has been detected in more than 90% of SS. [10] It results in the fusion of the SYT gene from chromosome 18 to one of three highly homologous genes at Xp11, namely, SSX1, SSX2, and, in rare instances, SSX4. [3],[5],[10] In our case, FISH analysis with SS18 probe confirmed the diagnosis of SS. FISH studies are relatively simple for pathologists and identify all the three fusion abnormalities. However, second locus involvement is detected by RT-PCR, however, this technique requires good mRNA yield from paraffin tissue, which is still a challenge. Kumar et al. used RT-PCR, which demonstrated the SYT-SSX1 fusion transcript, confirming the diagnosis of SS. SS with the SYT-SSX1 fusion transcript (irrespective of the histological type) has a poorer prognosis than cases with SYT-SSX2 fusion transcript. [10] TLE1 is promising IHC marker for diagnosis of SS especially where FISH facility is not available. In present understanding characteristic translocation identified by karyotyping, FISH or PCR is used as diagnostic test for confirmation. [11]
Primary pulmonary SS behaves more aggressively because of the late presentation, large tumor size and difficulty in achieving free surgical margins. In our case, lesion was very small and resected margins are free and these are favorable point for patient's prognosis. However, patient was lost to follow-up. Hartel et al. [4] had compiled data of five case series of primary pulmonary SS and mentioned that on an average 38% cases showed local recurrences and 42% died of disease within 5 years. Free surgical margins and adjuvant chemotherapy increases the time for local recurrence and disease-free survival. Nevertheless, the prognosis of primary pulmonary SS remains poor with an overall survival of 50%. [12] However, prognosis of primary endobronchial SS subset is not described.
| References | |  |
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[Figure 1], [Figure 2]
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