Review of Myofibroblastoma of Breast and Its Most Common Mimickers

Abstract

Myofibroblastoma (MFB) is characterized as a benign stromal neoplasm composed of uniform, bland-looking spindle cells that are often arranged in fascicles separated by thick band of collagenous stroma.  Variable cellularity is common.  Immunohistochemically, the spindle cells are positive for CD34, vimentin, BCL-2, ER, PR, focally positive for smooth muscle actin and negative for cytokeratin, S-100 and CD117.  Although classic MFB is typically a bland-looking spindle cell tumor, some unusual morphologic variants may show worrisome malignant-looking cells. Recognition of MFB variants and its wide variety of mimickers is very important for pathologists to arrive at the correct diagnosis, and avoid misdiagnosis of malignancy.