Cyto-Histopathological Findings of Myofibroblastoma of the Breast: A Case Report

Myofibroblastoma of the breast is a rare mesenchymal tumor, probably originating from stromal fibroblasts. In this case report, cyto-histopathological findings of myofibroblastoma of the breast are discussed. A 68-years-old male patient was admitted to our clinic with a rapidly growing, painless mass in the breast. Radiological examination revealed a mobile, solid mass resembling to fibroadenoma. Fine needle aspiration revealed spindle cell clusters with fibrous stroma and a clear background. Hypocellular aspirates demonstrated neoplastic cells with cyanophilic cytoplasm and mild/moderate pleomorphism, and naked elongated nuclei including fine granular chromatin, nuclear groove and inclusion. The lesion was reported as “benign spindle cell neoplasm”. Tru-cut biopsy revealed short fascicules composed of uniform benign spindle cells with hyalinized collagen bands accompanied by mast cells and patchy lymphoid infiltration. Immunoreactivity was positive with CD34, smooth muscle actin (SMA), desmin and vimentin, but negative with CD117, CD10, Epithelial Membrane Antigen, S-100, pan-cytokeratin and p53. This case was reported as “classic variant of myofibroblastoma”, and the patient was operated in another clinic. There was no recurrence during follow-up. Myofibroblastoma is a rare, benign mesenchymal tumor, usually seen in the breast parenchyma. While the tumor is diagnosed based on the fibro-myofibroblastic differentiation characteristics, other tumors and tumor-like spindle cell lesions should also be kept in mind. The cytological features of 22 cases in the literature were similar. Aspirates are generally hypercellular with mild-moderate pleopmorphism, nuclear groove and inclusions. Histopathology shows positivity for CD34, vimentin, desmin and SMA. Clinical/radiological characteristics and atypia, growth pattern, mitosis and immunohistochemistry should all be evaluated together. Cytomorphology may be the first step in diagnosis; however, immunohistochemical studies should not be ignored in differential diagnosis.