Low grade fibromyxoid sarcoma

Abstract

Although the histologic features of the recently described low grade fibromyxoid sarcoma are well established, to the authors' knowledge there are no reports in the literature describing the cytologic features of this tumor by fine-needle aspiration. Recognition of this lesion is important because of its indolent but metastasizing nature. The authors retrospectively reviewed their surgical pathology files for cases of low grade fibromyxoid sarcoma with a preoperative fine-needle aspiration biopsy (FNAB); three such cases were found. Immunohistochemical studies were performed in all three tumors, ultrastructural examination was performed in two tumors, and fresh tissue for cytogenetic analysis was obtained in one tumor. All FNABs showed similar features. The aspirates were relatively hypocellular with an abundant myxoid background; the neoplastic cells contained oval to spindle shaped nuclei with minimal pleomorphism. No capillaries or areas of fibrous tissue were identified. Cytogenetic study of one case revealed no chromosomal abnormalities. The histologic findings were characteristic for this lesion. By immunohistochemistry the tumor cells showed diffuse and strong reactivity for vimentin only; at the ultrastructural level the neoplastic spindle cells had characteristics of fibroblasts. The cytologic features of low grade fibromyxoid sarcoma are not specific enough for a definitive diagnosis based on FNAB alone; however, correlating the cytologic and clinical findings can narrow the range of diagnosis. The differential diagnosis includes other myxoid lesions, in particular superficial or intramuscular myxoma and myxofibrosarcoma. In addition, the immunohistochemical and ultrastructural findings support a fibroblastic origin for this neoplasm.