Cytopathology of extraskeletal myxoid chondrosarcoma: report of 8 cases

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft-tissue sarcoma rarely subjected to cytologic analysis. With the exception of a few small series, the cytology literature of EMC is largely limited to single-case reports. The purpose was to evaluate the cytomorphology of 8 EMC cases as obtained by imprint/scrape cytology and fine-needle aspiration (FNA) biopsy, to review the literature, and to demonstrate the utility of cytogenetic analysis in the diagnosis of EMC.

The cytology files were reviewed for all soft-tissue lesions signed out as chondrosarcoma, myxoid sarcoma, and EMC, and the tissue files for any cases of EMC that had corresponding cytopathology. FNA was performed using a standard technique. Scrape preparations were performed from tissue sent fresh to the laboratory for either frozen section or for special studies such as electron microscopy or tissue banking.

Eight cases of EMC were retrieved from 4 men and 3 women (median age = 62 years). One patient had 2 separate cytologic specimens 4.5 years apart. All patients had subsequent tissue confirmation of the diagnosis of EMC. Five individuals presented as new patients, and 2 had a prior diagnosis of EMC. Sites included 4 masses from the foot/ankle, 2 from the calf, 1 wrist mass, and 1 buttock mass. Five patients were diagnosed from FNA biopsy, whereas 3 were diagnosed using scrape slides. Five cases were correctly and categorically diagnosed by the cytologic method as EMC, 1 as chondrosarcoma favor EMC, 1 as sarcoma favor EMC, and 1 as myxoid spindle/epithelial neoplasm. Cytologic features ranged from hypocellular to highly cellular smears composed primarily of rounded cells set in an abundant myxoid stroma that varied from opaque to semitransparent and lacked vascularity or necrosis. Smears showed cells in short, sometimes anastomosing cords, but also as single cells and nondescript cell clusters. Cells displayed a monotonous uniformity in nuclear diameter and cell size. Bland nuclei with evenly dispersed chromatin displayed variably sized nucleoli, and a moderate amount of infrequently vacuolated cytoplasm. Tissue fragments of variable size were found in 5 of 5 FNA cell blocks. Fluorescence in situ hybridization (FISH) analysis using the EWSR1 probe showed a positive 22q12 translocation in 2 of 3 FNA cases that were tested. One case with negative FISH results on the cytologic preparation showed a positive translocation using the same technique in the subsequent resection specimen.

A confident cytologic diagnosis of EMC depends on the presence of a uniform, round to oval cell population often arranged in cords and set in an abundant myxoid/chondromyxoid background and arising in the appropriate clinical context. If positive, FISH testing (of paraffin cell blocks or cytospin preparations) is confirmatory when coupled with this cytomorphology.