Primary synovial sarcoma of the lung: a case report confirmed by moleculardetection 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 w as 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 cons istency. Histologically, the tumor showed a dense proliferation of short sp indle cells, partly arranged in interlacing fascicles; In some areas a hema ngiopericytoma-like pattern, stromal myxoid change and necrosis of various sizes were noted. Numerous mitotic figures were also seen. Immunohistochemi cally, the tumor cells were positive for epithelial markers such as cytoker atin and epithelial membrane antigen. As these features suggested a monopha sic fibrous type of synovial sarcoma, we examined for the presence of SYT-S SX fusion gene transcripts using RNA samples from the frozen tumor tissue. A reverse transcription polymerase chain reaction amplified a single 583-ba se pair fragment characteristic of synovial sarcoma. As no other tumorous l esions were found during a follow-up period of 1 year, primary synovial sar coma of the lung was our final diagnosis. This tumor should be considered i n the differential diagnosis of round to short spindle cell tumors arising in the lung.