Diagnostic pitfalls associated with fine-needle aspiration biopsy in a patient with the myxoid variant of monophasic fibrous synovial sarcoma

Abstract

Synovial sarcoma (SS) is one of the most common soft tissue tumors that typically presents in the extremities of young adults, but may occur at any site and affect children during the first decade. Herein we discuss a 12-yr-old male who complained of left foot pain and plantar mass. A fine-needle aspiration biopsy of an 8 cm subcutaneous mass was performed revealing a myxoid spindle cell neoplasm. The cytologic differential diagnosis included a myxoid neurofibroma, neurothekeoma, and a myxoid sarcoma. Subsequent excision of the mass revealed a monophasic fibrous SS with myxoid features. Examination of the tissue by fluorescence in situ hybridization confirmed the presence of characteristic SS SYT gene rearrangement at chromosome 18q11.2. This case underscores that the cytologic distinction of mxyoid spindle cell tumors may be challenging. We report the cytologic features of a myxoid monophasic fibrous SS, and discuss its distinction from other benign and malignant myxoid soft tissue neoplasms.

Contribution of Cytogenetics to the Management of Poorly Differentiated Sarcomas

“…Morphologic assessment of a spindle cell neoplasm can be complicated when the expected range of immunohistochemical markers or ultrastructural features are absent. Moreover, the immunohistochemical pattern for some spindle cell sarcomas, such as synovial sarcoma (SS) and malignant peripheral nerve sheath tumor (MPNST), can overlap with those of other neoplasms [46][47][48]. Detection of spindle cell sarcoma-specific translocations such as the SS-associated X;18 translocation, low-grade fibromyxoid sarcoma-associated 7;16 translocation, or 2p23 (ALK gene) rearrangements in inflammatory myofibroblastic tumor (to name a few) may be necessary to confirm a diagnosis in difficult cases.…”