A Case of Fibromatosis-like Metaplastic Carcinoma of the Breast

Abstract

A 61-year-old woman visited our hospital complaining of masses in her right breast and nipple. Both breast were assessed as category 1 on mammography. Ultrasonography revealed a 20 mm mixed tumor at the 9 o'clock position in the right breast. Contrast-enhanced MRI of the breast revealed a 14 × 19 × 18 mm mass with irregular margins and ring enhancement at the CD border of the right breast. Needle biopsy revealed a metaplastic carcinoma with a squamous cell component (luminal type). The patient was diagnosed with cT1cN0M0 stage I cancer. She underwent a partial mastectomy and a sentinel lymph node biopsy. Postoperative pathology revealed a diagnosis of pTN0M0 stage II A with mixed metaplastic carcinoma (squamous cell carcinoma with apocrine carcinoma and invasive ductal carcinoma [40%] and fibromatosis-like metaplastic carcinoma [FLMCa ; 60%]).

FLMCa is a histological type of low-grade spindle cell carcinoma. As the disease concept is new, the usefulness of postoperative adjuvant therapy remains unclear. Further understanding of the disease and careful follow-up observations are necessary for appropriate diagnosis and treatment.