Solitary extramedullary plasmacytoma of the tongue: a case report

Extramedullary plasmacytomas are rare solitary plasma cell neoplasms that occur outside the bone marrow. Primary tongue involvement is exceptionally uncommon and presents a significant diagnostic challenge. Their clinical presentation is often subtle and may closely mimic more common neoplastic processes.

We report the case of a 35-year-old man who presented with a gradually enlarging, firm, and painless mass on the ventral surface of the tongue that had been evolving for 5 months. Histopathological and immunohistochemical analyses revealed sheets of atypical plasma cells expressing CD38 and CD138 with kappa light-chain restriction, consistent with monoclonal plasma cell proliferation. A comprehensive systemic evaluation excluded multiple myeloma. The patient underwent definitive radiotherapy with a total dose of 50 Gy delivered in 25 fractions, resulting in complete remission without any functional impairment. At 9 months of follow-up, the patient showed no evidence of local recurrence or progression to multiple myeloma.

Primary extramedullary plasmacytoma of the tongue is exceptionally rare and may clinically mimic more common malignant or benign lesions, particularly in patients with a history of tobacco and alcohol exposure. An accurate diagnosis requires a multidisciplinary approach that integrates clinical findings, imaging, and histopathology, with immunohistochemical confirmation of monoclonality. Currently, radiotherapy remains the cornerstone of treatment, providing excellent local control and durable long-term remission.

This case underscores the exceptional rarity of primary extramedullary plasmacytoma of the tongue and highlights the effectiveness of radiotherapy as a curative and function-sparing treatment option for this condition, while emphasizing the necessity of long-term and lifelong surveillance to detect potential late recurrence or progression to multiple myeloma.