Primary intravascular synovial sarcoma: a disease of young adult women? Report of a case diagnosed by aspiration biopsy and review of the literature.

Intravascular synovial sarcoma (IVSS) is an extremely rare tumor with only four well-documented cases in the English literature. All tumors were located in large veins of the lower extremities or trunk in young women except for one case occurring in a 54-yr-old woman. We report here an additional case of IVSS arising from the superior vena cava in a 32-yr-old woman who presented with a cervical mass and superior vena cava syndrome. A fine-needle aspiration biopsy (FNAB) was performed and showed a malignant biphasic tumor with spindle cell and epithelioid components. The tumor cells were negative for CD31, CD34, factor VIII, desmin, smooth muscle actin, and S-100 protein, and had positive staining for vimentin and cytokeratin (AE1/AE3) predominantly in the spindle and epithelial components, respectively. A diagnosis of synovial sarcoma was made and confirmed in a subsequent transvascular biopsy demonstrating chromosomal translocation t(X, 18) by fluorescence in situ hybridization using a dual color, break-apart-style probe for SYT. Although clinically similar to previously reported IVSS, this is the first case arising in large veins of the upper portion of the trunk and diagnosed by FNAB.