DIAGNOSING INTRAMUSCULAR MYXOMA BY FINE-NEEDLE ASPIRATION - A MULTIDISCIPLINARY APPROACH

The gross and microscopic appearances of aspirates from ten intramuscu lar myxomas are reported, The specimens were obtained from seven women and three men, ages 43 to 75, who had tumors involving the muscles of the thigh (7), upper arm (2), and forearm (1). Magnetic resonance (MR ) imaging performed in six of the ten cases revealed well-defined, sha rply demarcated tumors exhibiting low signal intensity relative to mus cle on the TI-weighted images. The tumors were hyperintense to muscle on T2-weighted images. All aspirated tissues were clear, tenacious, an d viscous. Smears contained few spindled and histiocytoid cells in an abundant mucoid background. Spindle cells demonstrated long cytoplasmi c processes that in areas intertwined to form fibrillar tangles. Nucle i were oval to spindled with fine chromatin and inconspicuous nucleoli . Capillaries were sparse with simple (non-plexiform) branching. The d ifferential diagnosis of myxoid lesions of the extremities includes be nign en titles such as myxoid schwannoma and neurofibroma, mesenchymal repair, and ganglion cyst os well as malignant neoplasms such as myxo id liposarcoma, fibrosarcoma; malignant fibrous histiocytoma, and extr askeletal chondrosarcoma, The findings of this study revealed that, al though the cytologic features were suggestive of intramuscular myxoma a definitive diagnosis was often difficult, owing to scant cellularity and lack of distinctive cytologic features. The MR imaging findings m ay be utilized as an adjunct to the cytologic features to more confide ntly suggest a diagnosis of intramuscular myxoma. (C) 1994 Wiley-Liss, Inc.