A 79-year old woman with history of relapsed Stage II, grade III follicular lymphoma was treated with four cycles of rituximab and bendamustine with an excellent response. She was subsequently placed on maintenance rituximab infusions every eight weeks. Six months later, she presented to the dermatology clinic with a newly raised erythematous papule on her left cheek. Excisional biopsy confirmed a diagnosis of Merkel cell carcinoma which was resected with wide margins. Merkel cell carcinoma (MCC) is a rare aggressive skin malignancy, with a dramatic increase in incidence in the past few decades. It grows and metastasizes rapidly and diagnosis in early stages is often missed. Almost half of the patients with MCC have another active malignancy, compromising their immune system. Most commonly reported were cutaneous neoplasms, followed by leukemia and lymphomas. MCC is most common in caucasion population. Most affected patients are above 50 years old. Sun exposure is a major risk factor responsible for mutations created by ultraviolet-A radiation. In 2008, a novel discovery of Merkel cell polymavirus (MCPyV) was detected in most patients with MCC that plays a role in oncogenicity. Most primary lesions are aysmtomatic. Pathology findings of tumor size, depth, and lymphovascular invasion are important prognosticating factors. Further imaging modalities (CT, MRI and FDG-PET scans) are essential for staging. Treatment depends on the diagnosed stage. It varies from wide excision of the primary lesion followed by adjuvant radiation in early stages, to systemic chemo and immunotherapy. There have been two reported cases in literature about significant progression of Merkel cell carcinoma in patients concomitantly receiving rituximab as part of treatment for another malignancy. Which raises questions for future investigation whether there is a direct association between rituximab use specifically, and the rapid growth of MCC, or is it due to an immunocompromised state in general.
Antonios B, Herrman E, Chisti MM. Merkle cell carcinoma while on rituximab - is it a coincidence? Poster presented at: The American College of Physicians Michigan Chapter Residents Day / Medical Students Day; 2022 May 13; Dearborn, MI.