Fine-needle aspiration features of extraskeletal myxoid chondrosarcoma: A study of cytological and molecular features

Extraskeletal myxoid chondrosarcoma (EMC) is a tumor of uncertain differentiation. Few data are available regarding its cytomorphological features in fine-needle aspiration (FNA). Specific cytogenetic alterations involving the NR4A3 gene are found in EMC and can be identified in FNA samples.

We retrospectively reviewed 14 FNAs performed in 11 patients with an EMC; 10 FNAs were performed preoperatively on primary tumors; 2 were performed on recurrences and 2 were performed on metastasis. Cytological features were compared with histological findings. Immunohistochemistry (IHC) and molecular studies were performed both in FNA and histological specimens.

A preoperative cytological diagnosis of EMC was rendered in eight FNAs performed in newly diagnosed tumors and in recurrent/metastatic cases. A descriptive diagnosis of a myxoid neoplasm was made in the remaining two cases. Smears were moderately hypercellular, composed of plasmocytoid to fusiform cells, with scant, pale cytoplasm, bland nuclei and inconspicuous nucleoli, dispersed as cords, strands and occasionally with a lace-like pattern, in an abundant chondromyxoid matrix. IHC performed showed focal positivity for S100 and NSE. Fluorescence in situ hybridization technique performed in three FNA specimens showed EWSR1 gene rearrangements in all, concomitant with NR4A3 gene rearrangement in one case. Histological specimens showed typical features of EMC and NR4A3 gene rearrangements were found in all cases tested.

FNA cytology is a reliable method to perform a preoperative diagnosis of EMC regarding its cytomorphological and molecular features. Main differential diagnoses include myoepithelial tumors of soft tissue, myxoid liposarcoma and myxofibrosarcoma. Ancillary studies are helpful when coupled with cytomorphology evaluation.