Clinicopathological Features of Mammary Myofibroblastoma: A Single Institution Case Series.

Mammary myofibroblastoma (MFB) is a rare benign mesenchymal tumor of the breast with myofibroblastic differentiation. Its diverse morphological spectrum may pose diagnostic challenges, particularly in limited biopsy specimens. All MFB patients diagnosed at a tertiary care center between 2015 and 2024 were reviewed retrospectively. Eleven patients were identified, including 7 women and 4 men, with a mean age of 56.5 years (range: 31-75 years). All patients presented with a solitary, painless breast mass. Tumor size ranged from 2.3 to 14 cm. Histologically, 9 tumors showed spindle cell morphology, whereas 2 showed epithelioid features. The common findings included short intersecting fascicles of bland spindle cells, variable collagen deposition, ectatic blood vessels, and focal adipocytic components. Immunohistochemically, CD34 was positive in 9 tumors, desmin in 8, smooth muscle actin (ACTA2) in 5, BCL2 and CD99 in 7 each, and CD10 in 4 tumors. Keratin AE1/AE3, p63, S100, and STAT6 were negative in all tumors. Follow-up data was available in 9 patients and no recurrence was reported. Recognition of its characteristic morphological and immunohistochemical features is essential to avoid diagnostic pitfalls. Complete surgical excision is curative, with an excellent prognosis.