Fine-needle aspiration in myxofibrosarcoma: experience of Institut Curie

Myxofibrosarcoma (MFS) is a well-established nosologic entity different from the myxoid variant of malignant fibrous histiocytoma. In an attempt to better define the representative cytologic criteria of MFS, we undertook a review and a reanalysis of a series of 14 cytology samples in 12 patients whose tumors were diagnosed as MFS.Using FNA technique and reviewing the original diagnoses, 11 cases were diagnosed as malignant and three as benign tumors. The cytologic diagnosis of MFS was accurate in seven cases (2 primary tumors, 4 recurrences, and 1 metastasis). Four cases were classified malignant myxoid sarcoma (1 primary and 3 recurrences), whereas three cases (2 primary and 1 recurrence) were false-negative.The smears were cell-rich in 12 cases and cell-poor in two cases. They were constantly composed of isolated and regular small spindle-shaped and stellated cells with elongated nuclei containing small inconspicuous nucleoli. Cytoplasm was pale with elongated processes. Clusters of wavy spindle-shaped cells, round cells without specific pattern, moderate cytonuclear atypia, and abundant myxoid background as well as curvilinear vascular structures were always seen. In the vast majority of cases, the cytologic distinction of MFS from other low-grade myxoid lesions is difficult. Entities such as myxoid MFH, myxoid liposarcoma (MLP), myxoid DFSP, and myxoma should be considered in the differential diagnosis. The cytological misdiagnosis is of limited clinical consequence because FNA findings suggestive of a myxoid tumor will be indicative for a surgical removal followed by the histopathological analysis.