Transdifferentiation of Multiple Myeloma into Histiocytic Sarcoma: Case Report of a Highly Unusual Phenomenon.

ABSTRACT:

Introduction

Transdifferentiation of multiple myeloma (MM) into histiocytic sarcoma (HS) is exceptionally rare. We report a unique case, confirming this phenomenon through cytogenetics and molecular analyses.

Case presentation

A 46-year-old woman with high-risk light chain MM developed extramedullary disease despite multiple lines of therapy. Biopsies revealed atypical histiocytic proliferation consistent with HS. Shared immunoglobulin gene rearrangements, cytogenetic alterations, and gene mutations, including a rare BRAF L485F, confirmed clonal relatedness between the two neoplasms. IGH::MAF translocation specific to MM and IGVH somatic hypermutation in HS suggests divergent evolution from a putative germinal center B-cell (GCB) precursor.

Conclusions

This case highl

SUBMITTER: Seth N 

PROVIDER: S-EPMC12270463 | biostudies-literature | 2025 Jun

REPOSITORIES: biostudies-literature