Primary synovial sarcoma of the lung: report of two cases confirmed by molecular detection of SYT-SSX fusion gene transcripts

Aims: Primary pulmonary sarcoma is rare, and frequently creates diagnostic challenges, We describe two cases of primary pulmonary spindle cell sarcoma in which a molecular approach using archival paraffin-embedded tissue was proved to aid diagnosis. Methods and results: Both patients had huge masses replacing the upper and middle lobes of the lung, respectively, without any primary extrapulmonary neoplastic lesions, Microscopically, the lesions showed a solid hypercellul ar nodular or lobular growth of atypical short spindle cells in variably in tersecting fascicles or in a haphazard fashion, together with focal areas d isplaying a prominent haemangiopericytoma-like pattern. Immunohistochemical ly, a small number of the tumour cells were positive for epithelial markers such as cytokeratin and epithelial membrane antigen. In both cases, a reve rse transcription-polymerase chain reaction using RNA extracted from formal in-fixed, paraffin-embedded tissues detected SYT-SSX fusion gene transcript s, which are characteristic of synovial sarcoma, Conclusion: On the basis of the morphological and molecular findings, these tumours are considered to be rare examples of monophasic synovial sarcoma of the lung. Our molecular assay detecting the SYT-SSX fusion transcripts i s useful for the final diagnosis of synovial sarcoma arising at such an unu sual anatomical site.