Solitary Extraosseous Plasmacytoma of Submandibular Gland – Report of a Rare Case

Background: Plasmacytomas are tumors involving plasma cells that can be either osseous or extraosseous. Solitary extraosseous plasmacytomas are rarely found in the head and neck region. Various pathological, immuno-histochemistry, and radiological investigations must be done to distinguish it from multiple myeloma. Case: A 41-year-old female presented with a progressively increasing mass in right submandibular region for 1 year. She also had complaints of dysphagia and dyspnea for 3 months. Histopathological examinations showed lymphoplasmacytic infiltrate and possibility of plasma cell neoplasm was suspected. On further investigations like immunohistochemistry, bone marrow biopsy, quantitative immunoglobulin, immunoelectrophoresis, and urine analysis, diagnosis of extraosseous plasmacytoma was made. Positron emission tomography-computed tomography (PET-CT) scan did not show any distant foci of the disease. The patient received definitive radiotherapy to the primary region and tolerated well. The patient is asymptomatic after 1 month of radiotherapy and is on regular follow-up. Conclusions: Extraosseous plasmacytoma of the submandibular region is very rare but radiosensitive tumor. Multiple myeloma must be ruled out prior to start of any treatment. Long term follow ups are required to comment on disease progression, dissemination, or recurrence.