Chromosome 13q14 deletion in a mammary-type myofibroblastoma of the big toe—reply

Mammary-type myofibroblastoma of the thigh mimicking liposarcoma

Myofibroblastoma is a rare tumor that was originally described in the breast but has since been found in extra-mammary locations, where it been renamed mammary-type myofibroblastoma (MTM). We describe a case of MTM occurring in the anterior compartment of the thigh, which was initially interpreted as a possible a liposarcoma on MRI. Two subsequent biopsy samples and eventual excision revealed the tumor to have the characteristic pathology of MTM. This benign tumor, albeit rare, needs to be considered in the imaging differential diagnosis of fat containing deep soft tissue masses of the extremity.

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.

Mammary-Type Myofibroblastoma: A Report of Two Cases

Mammary-type myofibroblastoma (MFB) is a rare, benign spindle cell neoplasm occurring along the milkline, with extension from the mid-axilla to the medial groin. It is histologically and immunohistochemically identical to MFB of the breast and is part of a spectrum of lesions that includes spindle cell lipoma and cellular angiofibroma. Recently, we experienced two cases of mammary-type MFB involving male patients aged 30 and 58 years, respectively. The tumors were located in the right scrotal sac and in the right axilla. Wide excisions were performed. Microscopically, the masses were composed of haphazardly arranged, variably sized fascicles of bland spindle cells and were admixed with mature fat tissue. The spindle cells in both cases showed immunopositivity for desmin and CD34 and negativity for smooth muscle actin. Loss of retinoblastoma (RB)/13q14 loci is a characteristic genetic alteration of mammary-type MFB, and we identified loss of RB protein expression by immunohistochemical staining. We emphasize the importance of awareness of this rare neoplasm when a spindle cell neoplasm is accompanied by desmin immunopositivity. The second patient was alive without recurrence for 20 months, and the first patient had not been followed.