Intramuscular myxoma: MR features.

Intramuscular myxoma is a benign mesenchymal lesion consisting of bland spindled cells embedded in an avascular myxoid stroma. On CT, intramuscular myxoma presents as a well-demarcated, homogeneous, low density mass situated within skeletal muscle. The attenuation of the lesion is slightly greater than water but less than that of the surrounding normal muscle, with typical values between +10 and +60 HU. There is scant magnetic resonance (MR) literature on the appearance of intramuscular myxoma; the few MR spin echo images that have been published characterize it as a homogeneous mass with signal intensity less than or equal to skeletal muscle on T1-weighted and brighter than fat on T2-weighted pulse sequences. We present two cases of intramuscular myxoma with imaging characteristics that differ from those previously reported.