Cystic synovial sarcoma

A case of synovial sarcoma of the paraspinal region showing massive cystic changes is described. The tumor presented in a 53-year-old white woman who noticed a lump on the upper aspect of her back. Magnetic resonance imaging of the cervical spine showed a heterogeneous paraspinal mass with well-defined margins and a multilocular quality with foci of hemorrhage. Fine needle aspiration of the mass showed clusters of polygonal cells admixed with a scattered spindle cell component. Surgical excision of the mass showed a well-circumscribed but nonencapsulated tumor that showed multiple small cystic structures on cross-section. Histologic examination showed a biphasic neoplasm characterized by bland-appearing glandular elements embedded in a moderately cellular spindle cell stroma. The tumor contained multiple cysts of varying size. Immunohistochemical studies showed the glandular component to be positive for cytokeratin and epithelial membrane antigen. The spindle cell component was immunoreactive for cytokeratin, vimentin, bcl-2, and CD99. Stains for muscle-specific actin, smooth muscle actin, S-100 protein, and CD34 were negative. Cytogenetic analysis showed a balanced reciprocal translocation involving chromosomes X and 18, in addition to other clonal abnormalities. Synovial sarcoma should be considered in the differential diagnosis of cystic lesions involving the soft tissues. Magnetic resonance imaging is considered the procedure of choice for the evaluation of soft tissue tumors because of its superior soft tissue contrast and multiplanar imaging capability. While the imaging features of soft tissue tumors are often nonspecific, magnetic resonance imaging may provide helpful clues, thus narrowing the differential diagnosis. Immunohistochemical studies and cytogenetic analysis may be very helpful for establishing the correct diagnosis in cases with this unusual presentation. Ann Diagn Pathol 5:48-56, 2001.