Myofibroblastoma of the breast with hemangiopericytoma-like pattern and pleomorphic lipoma-like areas - Report of a case with diagnostic and histogenetic considerations

Myofibroblastoma (MFB) of the breast is an uncommon benign spindle cell tum or which may exhibit a wide spectrum of histological features. We report an unusual case of MFB of the male breast, showing cellular areas with a hema ngiopericytoma-like pattern similar to that observed in solitary fibrous tu mor (SFT) and extensive fibromyxoid areas containing numerous atypical stro mal cells. The association of these atypical cells with mature adipocytes a nd microcystic and/or myxoid degenerative changes resembled pleomorphic lip oma-like and myxoid liposarcoma-like features, respectively. To our knowledge, these peculiar morphological findings have not been previ ously reported in MFB of the breast. They should be recognized to avoid con fusion with other mesenchymal tumors, especially with hemangiopericytoma, p leomorphic lipoma (PL), spindle-cell lipoma (SCL) and myxoid liposarcoma. A case of MFB of the breast showing morphological features also commonly se en in SFT and PL/SCL is further morphological evidence in support of the sp eculation that the mesenchymal tumors of the breast, also known under the t erms benign spindle cell tumors, fibromas, SFTs, SCLs and MFBs, are histoge netically related lesions.