Recurrent synovial cyst of deep soft tissues - A case report

BACKGROUND: Cystic lesions of deep soft tissues are rare and usually are co mposed of a mesenchymal tumor undergoing necrosis or regressive changes. Be nign cysts arising de novo are even mauls rave and may show features of dif ferent morphology, potentially leading to an inexact diagnosis. CASE: A 68-year-old male presented with a deep, firm mass in the upper part of the back from which a dense liquid was aspirated, with an inconclusive diagnosis. A second fine needle aspiration was performed and the lesion was surgically biopsied. Immunohistochemical studies were also inconclusive, w hile ultrastructural studies suggested an origin in the synovia of the scap ular bursa. CONCLUSION: The cytologic picture was suspicious for malignancy due to the presence of numerous pseudopapillary structures, reminding us of a secondar y deposit from a renal or thyroid primary or mesenchymal neoplasm. However, the bland nuclear aspect suggested the benignity of the lesion, and the el ectron microscopic features confirmed the synovial origin.