Cytogenetics as an adjunct in establishing a definitive diagnosis of synovial sarcoma by fine-needle aspiration

Synovial sarcomas account for up to 10% of all soft tissue sarcomas and are characterized by a specific chromosomal abnormality, t(X; 18)(p11.2; q11.2), that is observed in both monophasic and biphasic variants.

A 9-cm suprascapular mass in a 43-year-old man and a 10-cm leg mass in a 45-year-old man were aspirated. Rapid evaluation of air-dried Diff-Quick-stained smears in both cases showed a malignant spindle cell lesion. Cytogenetic material was collected in RPMI 1640 tissue culture medium. Additional alcohol-fixed slides and cell blocks were prepared on both cases. Immunohistochemical studies were performed on paraffin embedded cell block sections in both cases whereas electron microscopic examination was performed in one case. G-banded chromosome preparations from tumor cells were made after short term culture using standard cytogenetic techniques.

Evaluation of the smears showed densely cellular and tightly cohesive malignant spindle cells without discernible epithelial differentiation. A differential diagnosis of synovial sarcoma, leiomyosarcoma, malignant schwannoma, and fibrosarcoma was considered. Immunohistochemical stains and electron microscopy were noncharacteristic and noncontributory in establishing a diagnosis. However, cytogenetic results revealed a t(X; 18)(p11.2; q11.2) translocation, thus establishing the diagnosis of synovial sarcoma. Both patients were offered definitive therapy based on fine-needle aspiration (FNA) diagnosis only.

FNA can be used effectively to obtain karyotypes of sarcomas. The specific cytogenetic abnormality associated with synovial sarcoma provides an opportunity to make definitive diagnoses using a combination of FNA and cytogenetics, obviating open surgical biopsy preceding therapy.