# MAML2‐Rearranged Hidradenoma of the Breast: Clinicopathologic and Molecular Analysis of Four Patients

## TL;DR

This study examines four cases of a rare breast tumor called hidradenoma and finds that all cases show a specific genetic change, which could help in accurate diagnosis and avoiding unnecessary treatment.

## Contribution

The study identifies MAML2 gene rearrangement as a defining feature of hidradenoma in the breast, offering a potential diagnostic marker.

## Key findings

- MAML2 rearrangement was detected in all four cases of breast hidradenoma using FISH.
- Breast hidradenoma often mimics malignancy and is frequently diagnosed only after surgical removal.
- Recognizing the clinicopathologic and molecular features of breast hidradenoma can prevent overtreatment.

## Abstract

Hidradenoma (HA) is a rare, benign adnexal tumor typically arising in the skin, with only a few reported cases in the breast. Histologically, HA displays solid and cystic patterns with diverse cellular components. Although MAML2 gene rearrangement is observed in some cutaneous HAs, its significance in breast HA remains unclear. We retrospectively analyzed four cases of breast HA at our institution, focusing on clinicopathologic and molecular characteristics. MAML2 rearrangement was detected in all cases by FISH, suggesting it may be a defining feature of breast HA. Because breast HA frequently mimics malignancy and is often diagnosed only after excision, heightened awareness and recognition of its distinctive clinicopathologic and molecular features are essential to prevent overtreatment.