breast myofibroblastoma

Mammary myofibroblastoma

Mammary myofibroblastoma (MFB), also named mammary and extramammary myofibroblastoma, was first termed myofibroblastoma of the breast, or, more simply, either mammary myofibroblastoma or just myofibroblastoma. The change in this terminology occurred because the initial 1987 study and many subsequent studies found this tumor only in breast tissue. However, a 2001 study followed by numerous reports found tumors with the microscopic histopathology and other key features of mammary MFB in a wide range of organs and tissues. Further complicating the issue, early studies on MFB classified it as one of various types of spindle cell tumors that, except for MFB, were ill-defined. These other tumors, which have often been named interchangeably in different reports, are: myelofibroblastoma, benign spindle cell tumor, fibroma, spindle cell lipoma, myogenic stromal tumor, and solitary stromal tumor. Finally, studies suggest that spindle cell lipoma and cellular angiofibroma are variants of MFB. Here, the latter two tumors are tentatively classified as MFB variants but otherwise MFB is described as it is more strictly defined in most recent publications. The World Health Organization in 2020 classified mammary myofibroblastoma tumors and myofibroblastoma tumors (i.e. extramammary myofibroblastic tumors) as separate tumor forms within the category of fibroblastic and myofibroblastic tumors. Mammary MFB likely represents less than 1% of all breast tumors. Extramammary MFB, however, has in recent studies been found to occur far more frequently than mammary MFB: a study of 143 patients re...