# Fibromatosis-like metaplastic carcinoma with aggressive metastasis and a TERT promoter mutation: a case report and literature review

## TL;DR

A rare breast cancer case showed aggressive metastasis and a TERT promoter mutation, challenging its usual indolent behavior.

## Contribution

This case report identifies an aggressive FLMCa with a TERT promoter mutation, suggesting a new molecular mechanism for its virulence.

## Key findings

- The patient developed lung and bone metastases within 15 months despite multimodal therapy.
- A TERT promoter C228T mutation was identified as a potential driver of aggressive behavior.
- The case suggests a need for revised risk stratification and molecular profiling in FLMCa.

## Abstract

Fibromatosis-like metaplastic carcinoma (FLMCa) is a rare, typically indolent subtype of triple-negative breast cancer. This report presents an exceptional case of FLMCa with an aggressive clinical course, challenging the conventional understanding of its low metastatic potential.

A 57-year-old woman presented with a left breast mass. The diagnosis was confirmed via histopathology and immunohistochemistry. Sanger sequencing was used to investigate potential genetic drivers.

Pathological examination confirmed FLMCa, characterized by bland spindle cells and a triple-negative immunophenotype. A genetic analysis revealed a C228T mutation in the telomerase reverse transcriptase (TERT) promoter region. Despite multimodal therapy, including surgery, radiotherapy, and multiple lines of chemotherapy, the patient developed lung metastasis at 5 months and bone metastasis at 15 months post-surgery.

This case highlights that a subset of FLMCa may exhibit unexpectedly aggressive behavior and resistance to conventional therapy. The presence of a TERT promoter mutation suggests a potential molecular mechanism for this virulence. Our findings advocate for a re-evaluation of risk stratification in FLMCa and underscore the critical need for vigilant follow-up and molecular profiling to guide future targeted therapy strategies.