Fibromatosis-Like Metaplastic Carcinoma of the Breast: A Challenging Diagnosis With Potential Pitfalls

• Published in: International journal of surgical pathology 2024-12, p.10668969241300498
• Main Authors: Laokulrath, Natthawadee, Gudi, Mihir Ananta, Tan, Puay Hoon, Tan, Tessa Ying Zhen, Lim, Geok Hoon
• Format: Article
• Language: English
• ISSN: 1940-2465; 1940-2465
• DOI: 10.1177/10668969241300498

Fibromatosis-like metaplastic carcinoma (FLMC) is a rare subtype of metaplastic carcinoma of the breast. Diagnosing this entity poses significant challenges, particularly in core biopsies due to limited sampling and overlap with benign spindle cell lesions such as nodular fasciitis and fibromatosis. We present an example of FLMC in an asymptomatic middle-aged woman. As her breast imaging revealed an irregular lobulated mass, a core biopsy was performed which showed benign breast tissue with fibrosis. However, this was discordant with her imaging findings, hence a subsequent vacuum-assisted biopsy was done which revealed low-grade spindle cell proliferation, consistent with FLMC. This report emphasizes the necessity of a triple assessment and highlights the potential pitfalls in diagnosing FLMC, particularly the risk of misinterpretation due to its histological similarities with benign entities. Understanding these challenges will be crucial to avoid diagnostic delays of this rare breast cancer subtype.