Diffuse Large B-Cell Lymphoma Presenting as an Infiltrative Masticator Space Lesion Mimicking Inflammatory Disease: A Case Report.

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma in adults. Although extranodal involvement is frequent, presentation as an infiltrative lesion of the masticator space is rare and may mimic inflammatory, odontogenic, salivary gland, or soft tissue disorders, leading to diagnostic delay. We report the case of a 34-year-old woman who presented with progressive right mandibular swelling, facial paresthesia, trismus, weight loss, and night sweats. Initial computed tomography suggested an inflammatory process, whereas magnetic resonance imaging revealed an infiltrative lesion involving the right masticator space, deep lobe of the parotid gland, and ipsilateral cervical lymph nodes. Fine-needle aspiration and an initial biopsy were inconclusive, requiring excisional lymph node biopsy for definitive diagnosis. Histopathological examination confirmed germinal center B-cell-type DLBCL associated with high-grade follicular lymphoma and CD30 expression. The patient was classified as having limited-stage disease and received four cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) chemotherapy, achieving complete metabolic remission. More than three years after treatment completion, she remains disease-free. This case highlights the importance of including lymphoma in the differential diagnosis of infiltrative lesions of the masticator space and emphasizes the need for adequate tissue sampling when initial investigations are inconclusive.