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

Introduction: 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. Case Report: 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. Conclusion: 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.