Progressive growth of primary synovial sarcoma of the lung

An 80-year-old male was admitted because of a giant mass in the left lower lobe of the lung on a routine chest X-ray. Chest computed tomography verified this to be a well-defined heterogeneous mass as described with no associated lymphadenopathy. FDG-PET depicted moderately marginal FDG uptake. The patient underwent a left lower lobectomy and lymphadenectomy. Grossly, the tumor measured 60 × 50 mm and was uniformly filled with a pure white, pudding-like friable substance. No lymph node metastasis was observed microscopically. Histologically, the tumor showed a dense proliferation of rounded or spindled malignant cells with a frequent mitotic activity and an increased nuclear-to-cytoplasmic ratio. The immunohistochemical staining was positive for vimentin, negative for cytokeratin, keratin-wide, EMA, CD34. A SYT-SSX2 fusion gene transcript was detected as a result of RT-PCR analysis. Because of these results, the tumor was diagnosed as a monophasic synovial sarcoma.