Diffuse large B-cell lymphoma of the parotid gland: Cytological, histopathological, and immunohistochemical features: A rare case report

Primary malignant lymphomas of the salivary glands are rare, accounting for 2-5% of salivary gland tumors and 5% of extranodal lymphomas, frequently seen in the parotid gland. There are single case reports mentioned in the literature. Clinical presentation is not characteristic and the disease is often overlooked with delay in diagnosis and treatment. We are reporting a case of bilateral parotid gland lymphoma in a 55-year-old male, presented with bilateral enlarged parotids. Magnetic resonance imaging (MRI) showed bilateral enlarged parotid glands with multiple well-defined intraparotid lesions. Fine Needle Aspiration Cytology (FNAC) of both showed mixed population of lymphoid cells with large monocytoid cells with scant cytoplasm, anisonucleosis with prominent nucleoli, and numerous mitoses suggestive of non-Hodgkin's lymphoma (NHL). Histopathology showed sheets of large lymphoma cells destructing the salivary acini and infiltrating the periparotid fat. Immunohistochemistry (IHC) showed diffuse CD20 positivity, B-cell lymphoma 6 protein (Bcl-6) was focally positive and negative for cluster of differentiation (CD) 3, CD5, CD10, and Multiple myeloma oncogene-1 (MUM1) which led to the diagnosis of NHL-Diffuse large B cell type.