# Follicular Lymphoma of the Breast With Secondary Central Nervous System Transformation and Concurrent Metastatic Melanoma: Report of a Rare Case

## TL;DR

This paper reports a rare case of breast follicular lymphoma that transformed in the brain and co-occurred with metastatic melanoma, highlighting the challenges of managing such complex dual cancers.

## Contribution

The novelty lies in documenting the rare coexistence of CNS-transformed follicular lymphoma and metastatic melanoma, along with the management approach.

## Key findings

- The patient had breast follicular lymphoma that transformed into CNS diffuse large B-cell lymphoma.
- Metastatic melanoma was concurrently diagnosed, requiring a tailored treatment approach.
- The case was managed as primary CNS lymphoma with a focus on quality of life despite progression.

## Abstract

Follicular lymphoma (FL) rarely presents in the breast and even less frequently transforms with secondary central nervous system (CNS) involvement. The coexistence of transformed FL with metastatic melanoma is exceptionally rare and presents significant diagnostic and therapeutic challenges. We report the case of an elderly female initially diagnosed with primary breast follicular lymphoma (FL), managed with surveillance. Over subsequent years, she experienced multiple relapses, treated with bendamustine-rituximab and later lenalidomide, achieving remission. Fourteen years after initial diagnosis, she developed CNS symptoms with cerebellar lesions; resection revealed transformed diffuse large B-cell lymphoma (DLBCL) of germinal center origin (CD5+, CD10+, BCL2, BCL6, MYC+, Ki-67 ~70%). Concurrent metastatic melanoma was also diagnosed. Given the rarity of CNS-transformed FL and the absence of standard guidelines, her case was managed as primary CNS lymphoma. She received high-dose methotrexate, rituximab, and temozolomide with Stereotactic Body Radiotherapy (SBRT) for melanoma. Despite significant intracranial progression, she remained largely asymptomatic and prioritized quality of life, highlighting the challenges of individualized care in complex dual malignancies.