# Mantle Cell Lymphoma Mimicking Parotid Neoplasm: A Rare Case Report

## TL;DR

A rare case of mantle cell lymphoma presenting as a parotid gland tumor is reported, emphasizing the need for early diagnosis to avoid delays in treatment.

## Contribution

This case report highlights the unusual presentation of mantle cell lymphoma in the parotid gland and its diagnostic challenges.

## Key findings

- Mantle cell lymphoma can present as a parotid gland mass, mimicking benign conditions.
- Immunohistochemical profiling confirmed the diagnosis with specific marker positivity and negativity.
- PET-CT identified systemic disease, guiding the initiation of chemotherapy.

## Abstract

Mantle cell lymphoma (MCL) is a rare and aggressive B-cell non-Hodgkin lymphoma, commonly affecting lymph nodes, spleen, bone marrow, and gastrointestinal tract. Salivary gland involvement, especially in the parotid gland, is unusual and often mimics benign conditions, complicating diagnosis.

A 58-year-old male presented with a painless, progressively enlarging swelling in the right preauricular region without facial nerve involvement. Imaging revealed a mass within the parotid gland, leading to superficial parotidectomy. Histopathology confirmed mantle cell lymphoma. Immunohistochemical studies showed positivity for CD20, BCL2, CD5, and Cyclin D1; negativity for CD23, CD10, BCL6, and MUM1; and scattered CD3-positive T lymphocytes. The Ki-67 proliferation index was approximately 40%, indicating intermediate proliferative activity. Whole-body PET-CT revealed additional metabolically active lesions suggestive of systemic disease. The patient was started on bendamustine and rituximab chemotherapy.

This case highlights that parotid swellings may conceal systemic lymphomas, and misleading cytology can delay diagnosis. Clinicians should consider MCL in atypical parotid lesions to ensure early systemic therapy.