Mammary-type myofibroblastoma of the liver: multi-modality imaging features with histopathologic correlation

A 46-year-old woman with an incidentally discovered hepatic mass at the time of echocardiography underwent additional imaging for characterization. Ultrasound demonstrated a 5.3 cm solid hyperechoic mass. Computed tomography and magnetic resonance imaging showed intratumoral fat and nodular foci of progressive enhancement. The patient underwent surgical resection, with the mass demonstrating histopathologic and immunohistochemical features diagnostic of a hepatic mammary-type myofibroblastoma. We present herein the clinical, imaging, and pathologic features in this unique case of hepatic mammary-type myofibroblastoma. Mammary-type myofibroblastoma is a benign spindle cell tumor typically composed of groups of myofibroblasts within bands of hyalinized collagenous stroma. Some tumors also have an adipocytic component. The tumor is nearly exclusively seen in the breast and although extramammary soft tissue locations have been described, to our knowledge, this is the first reported case in the liver or any visceral site. Although rare, radiologists and clinicians should, therefore, be aware of the possibility of a mammary-type myofibroblastoma when a solid, non-encapsulated, fat containing tumor in the liver is encountered.