PRIMARY PULMONARY SARCOMA WITH MORPHOLOGIC FEATURES OF MONOPHASIC SYNOVIAL SARCOMA AND CHROMOSOME-TRANSLOCATION T(X-18)

The authors report an unusual spindle cell sarcoma that arose in the l ung of a 12-year-old girl. This tumor had histologic, immunophenotypic , and ultrastructural features consistent with monophasic fibrous syno vial sarcoma. These features included a growth pattern of densely pack ed spindle cells in irregularly intersecting, broad fascicles, diffuse vimentin immunoreactivity, and focal expression of epithelial membran e antigen and S100 protein. This diagnosis was further supported by cy togenetic studies showing the specific t(X; 18) chromosomal translocat ion associated with synovial sarcoma. This balanced translocation appe ars to be an essentially universal characteristic of these sarcomas, r egardless of histologic subtype or site of origin. The constellation o f morphologic and cytogenetic findings in this case firmly establishes synovial sarcoma as a subtype of pulmonary spindle cell sarcomas. The distinctive features of these neoplasms allow them to be distinguishe d from a variety of primary and metastatic malignancies in the lung.