Development of Merkel Cell Carcinoma in a Patient Receiving Rituximab

Abstract

Merkel cell carcinoma (MCC) is a rare, rapidly growing, and aggressive dermatological neoplasm. It is commonly reported in Caucasian ethnicities, and almost 50% of the patients have a concomitant malignancy and are on immunosuppressive chemotherapy. Here, we present a 79-year-old woman with a history of relapsed Stage II, grade III follicular lymphoma, receiving maintenance rituximab infusions. She presented with a raised erythematous papule on her left cheek. An excisional biopsy of the lesion confirmed a diagnosis of Merkel cell carcinoma. After which, she underwent a wider excision with 1-2 cm margins. PET scan did not reveal any FDG-avid uptake lesions that would be concerning for metastatic disease. However, she underwent a sentinel lymph node biopsy which was also negative. Thus, the diagnosis was finalized as Stage I (T1 N0 M0) MCC. There are only two reported cases in literature about the significant progression of Merkel cell carcinoma in patients who coincidentally were receiving rituximab as a part of treatment for another disease. This raises questions for future investigation and research on whether there is a direct association between rituximab use specifically and the rapid growth of MCC.

A Challenging Diagnosis of Merkel Cell Carcinoma Occurring in the Lymph Nodes and Skin of a Patient with Mantle Cell Lymphoma: A Case Report

“…In the current case we prioritized MCC treatment (with pembrolizumab) given the greater involvement of MCC in the lymph nodes. Furthermore, this recognition helped avoid the usual treatment of rituximab for MCL, which has been associated with rapid growth of MCC (11)(12)(13)(14). Skin cancer patients with concurrent haematological malignancies also tend to have lower response rates to anti-PD-1 immunotherapy, which is first-line for unresectable MCC (15).…”