# How Early Is Too Early? Use of Lineage-Specific Chimerism in Early Detection of Donor-Derived Malignancy After Allogeneic Stem Cell Transplant: A Case Report

## TL;DR

A case report shows how early chimerism monitoring helped detect a rare donor-derived cancer after a stem cell transplant.

## Contribution

Demonstrates the potential of lineage-specific chimerism analysis for early detection of donor-derived malignancy.

## Key findings

- Loss of a satellite marker in chimerism analysis predicted donor-derived malignancy six months before symptoms.
- Early detection through chimerism monitoring could allow earlier intervention in similar cases.

## Abstract

Allogeneic stem cell transplant is critical for treatment of certain hematologic malignancies. However, it has significant risks including relapsed malignancy, infection, and graft versus host disease. Rarely, de novo malignancy can arise from donor cells. Chimerism analysis is used to monitor engraftment and predict rejection or disease relapse. Our patient underwent an allogeneic transplant for myelodysplastic syndrome but had persistent pancytopenia despite donor lymphocyte infusion. This was due to donor-derived malignancy, which was predicted by loss of a satellite marker on chimerism analysis 6 months prior. This could have allowed earlier intervention and underscores the importance of detailed chimerism monitoring.