Primary synovial sarcoma of the lung: a case report confirmed by molecular detection of SYT-SSX fusion gene transcripts.

We report a rare case of primary synovial sarcoma of the lung. The patient was a 49-year-old woman who presented with a well-defined oval-shaped mass in the left upper lobe on a chest radiograph. A malignant pulmonary tumor was suspected and consequently a left upper lobectomy was performed. Grossly, the tumor measured 5 x 4 cm, was whitish-yellow in color and soft in consistency. Histologically, the tumor showed a dense proliferation of short spindle cells, partly arranged in interlacing fascicles. In some areas a hemangiopericytoma-like pattern, stromal myxoid change and necrosis of various sizes were noted. Numerous mitotic figures were also seen. Immunohistochemically, the tumor cells were positive for epithelial markers such as cytokeratin and epithelial membrane antigen. As these features suggested a monophasic fibrous type of synovial sarcoma, we examined for the presence of SYT-SSXfusion gene transcripts using RNA samples from the frozen tumor tissue. A reverse transcription polymerase chain reaction amplified a single 583-base pair fragment characteristic of synovial sarcoma. As no other tumorous lesions were found during a follow-up period of 1 year, primary synovial sarcoma of the lung was our final diagnosis. This tumor should be considered in the differential diagnosis of round to short spindle cell tumors arising in the lung.