# Spontaneous Resolution of Follicular Lymphoma in an Elderly Caucasian Patient Undergoing Uninvolved Radiation Therapy for Recurrent Merkel Cell Carcinoma: A Case Report

## TL;DR

An elderly patient with Merkel cell carcinoma and follicular lymphoma experienced complete lymphoma remission after radiation therapy for the carcinoma, possibly due to an abscopal effect.

## Contribution

This case report is the first to document follicular lymphoma resolution via abscopal effect from radiation therapy targeting a different cancer.

## Key findings

- Radiation therapy for Merkel cell carcinoma led to complete clearance of uninvolved-site follicular lymphoma.
- The abscopal effect may have caused the destruction of follicular lymphoma in uninvolved sites.
- This is the first reported case of such cross-tumor response via radiation therapy.

## Abstract

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous malignancy with an annual incidence rate of less than one case per 100,000 person-years in the United States, up to 59% of which have a reported risk of loco-regional and distant metastasis. While wide local excision with sentinel lymph node biopsy is the gold standard for the initial management of localized MCC, adjuvant radiation therapy is commonly utilized as a supplemental treatment modality for these patients as well. Here we present the case of a Caucasian woman in her 90s with recurrent MCC and concurrent grade 3A follicular lymphoma who received 6700 cGy of radiation therapy over two months for her recurrent MCC, which led to complete clearance of her uninvolved-site follicular lymphoma likely via an abscopal effect. While its exact mechanism needs to be further studied, the abscopal effect is thought to be a process in which radiation therapy of a malignant proliferation leads to destruction of the same malignancy in uninvolved sites. However, to our knowledge, the resolution of uninvolved-site follicular lymphoma in response to radiation therapy of a different malignancy such as MCC is not previously reported.