[Poorly differentiated synovial sarcoma of the chest wall with rhabdoid features]. / Sarcoma sinovial pobremente diferenciado de pared del tórax con características rabdoides.

We report a rare case of a poorly differentiated synovial sarcoma (SS) with rhabdoid features. A 33-year-old woman was referred to our hospital with a chest wall tumor. MRI revealed a diffuse mass that invaded the pleura and extended into the esophagus, aorta, diaphragm and pancreas. Histopathological examination of the neoplasm showed it to be composed of sheets of small/medium cells with rhabdoid morphology, consisting of round, eccentrically localized nuclei, conspicuous nucleoli, and eosinophilic cytoplasm. Immunohistochemical studies demonstrated the tumor cells to be positive for TLE1, Bcl-2, EMA, CAM5.2, CD138 and CD56 and negative for desmin, smooth muscle actin or S100 protein. Fluorescent in-situ hybridization technique, performed on the paraffin section, showed SS18 gene rearrangement in the nuclei of the tumor cells. Poorly differentiated SS with "rhabdoid" features was diagnosed. This is only the 8th case of a SS with "rhabdoid" features reported to date.