A Case of Myofibroblastoma in Male Breast

Yanagihara K, Yamakawa T, Kato S, Tamura M, Ueda K and Kanazawa Y

Published on: 2025-03-11

Abstract

Myofibroblastoma of the breast is a rare benign disease that was first reported by Wargotz et al. in 1987.It tends to occur in middle-aged and elderly people in whom a malignant tumor is suspected clinically, and it is diverse both in terms of imaging and histology. In some cases, surgery is performed as if it were malignant without a definitive diagnosis. In this case, we report a case in which we performed a surgical removal of a mass in the left breast, believing it to be myofibroblastoma and underwent a surgical removal.

A 76-year-old male patient with slight cough came to our hospital. CT scan for coughing symptoms revealed a mass in the left breast. A 4 cm mass was palpable in the upper outer area of the left breast, slightly distant from the nipple. It had a hardness similar to that of a lipomatous lesion. Mammography showed a high-density mass with irregular margins in the upper outer area of the left breast.

Ultrasonography showed a hypoechoic mass. The internal echo was relatively uniform, the boundary was irregular in part, and it was accompanied by a thick halo. Fine-needle aspiration cytology revealed spindle cells, it was difficult to distinguish (Class III). Histopathological findings of needle biopsy showed a bundle-like proliferation of spindle-shaped cells with elongated eosinophilic cytoplasm and oval or round nuclei was seen between collagen fibers. And spindle-shaped cells with oval or round nuclei were seen in bundles. Immunostaining showed that the tumor was positive for estrogen receptor (ER) and progesterone receptor (PgR), Ki67 was positive in about 1% of the cells, and it was negative for cytokeratin (AE1/AE3, CK5/6) and p63.

The possibility of a mesenchymal tumor, particularly a myofibroblastoma, was considered, and additional immunostaining was performed. In spindle-shaped cells, desmin was positive, CD34 was positive, STAT-6 (negative in the nucleus, positive only in the cytoplasm), β-catenin (negative in the nucleus, positive only in the cytoplasm), and EMA were almost negative, findings that supported a myofibroblastoma. We report a case in which a myofibroblastoma diagnosed before surgery.