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Primary endobronchial synovial sarcoma

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.[4-8] It offers a diagnostic challenge, and is often misdiagnosed as either a primary pulmonary spindle cell sarcoma/carcinoma or metastatic sarcoma.[4-7] 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.