Epithelioid myofibroblastoma of the breast: A case report and review of the literature

Takahiro Inaishi; Takahiko Sakuma; Tomoki Fukuoka; Shu Ichihara

doi:10.1016/j.ijscr.2022.107382

Epithelioid myofibroblastoma of the breast: A case report and review of the literature

Int J Surg Case Rep. 2022 Jul:96:107382. doi: 10.1016/j.ijscr.2022.107382. Epub 2022 Jul 2.

Authors

Takahiro Inaishi¹, Takahiko Sakuma², Tomoki Fukuoka³, Shu Ichihara⁴

Affiliations

¹ Department of Breast and Endocrine Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, Japan.
² Department of Diagnostic Pathology, Toyohashi Medical Centre, 50 Hamamichi-Gami, Imure, Toyohashi, Aichi, Japan. Electronic address: sakuma.takahiko.bu@gmail.com.
³ Department of Surgery, Nagoya Memorial Hospital, 4-305 Hirabari, Tenpaku-ku, Nagoya, Aichi, Japan.
⁴ Department of Pathology, Nagoya Medical Centre, 4-1-1 Sannomaru, Naka-ku, Nagoya, Aichi, Japan.

Abstract

Introduction: Mammary myofibroblastoma (MFB) is a rare tumour. Its clinical and pathologic characteristics have been only sporadically described. A case of epithelioid variant of MFB is reported with the diagnostic tips, the differential diagnoses, and a discussion on the possible pathogenesis.

Presentation of case: A 74 year-old woman presented with a painless nodule in the left breast. Core needle biopsy (CNB) revealed a tumour primarily composed of epithelioid cells. Despite epithelioid appearance of the tumour cells, ductal/lobular components were absent within the tumour. As cell lineage of the epithelioid cells could not be determined with CNB, lumpectomy was performed to obtain definitive diagnosis and, at the same time, to remove the lesion. Histologically, the tumour consisted of multiple epithelioid cell nests that were spread over fibrous stroma infiltrated with adipose tissue. Spindle cells were also present, but they were fewer than epithelioid cell clusters. Occasionally, the tumour cells showed nuclear atypia. It was difficult to determine whether this tumour was benign or malignant solely with Hematoxylin-eosin stain. However, with the aid of immunohistochemical analyses, we could make a histodiagnosis of epithelioid subtype of myofibroblastoma.

Discussion: The differential diagnoses of epithelioid MFB include ductal, lobular, metaplastic carcinomas and mesenchymal tumours. Comprehensive knowledge of classic and variant MFB is necessary for the correct diagnosis.

Conclusion: Pathologic diagnosis of epithelioid variant of MFB requires careful evaluation of histology and the use of a panel of immunohistochemistry. Female phenotype of breast stroma may play a role in the pathogenesis of MFB.

Keywords: Breast; Epithelioid variant; Immunohistochemistry; Myofibroblastoma.