Imaging features of mammary-type myofibroblastoma of soft tissue: a case series with literature review

Mammary-type myofibroblastoma (MTM) is a rare, benign neoplasm that is histologically identical to myofibroblastoma of the breast, but occurring in an extramammary site. The masses have been reported in superficial and deep soft tissue sites and visceral locations with the inguinal area and lower extremities are the most common. Most previous reports of MTMs have concentrated on clinical and pathological findings, with very limited information regarding imaging characteristics. Here, we describe three cases of MTM diagnosed at our institution, with a focus on imaging findings. We compare our findings with previously reported cases. Although MTM is rare, radiologists should be aware of this benign diagnosis as imaging characteristics can mimic those of liposarcomas and atypical lipomatous tumor/well-differentiated liposarcoma. Unlike those tumor types, MTM virtually never recurs post-resection, even when there are positive margins. Biopsy is necessary for proper diagnosis and recommended as an initial step to avoid overly aggressive treatment.