Exclusive Radiotherapy in the Management of Mandibular Solitary Plasmacytoma: A Rare Case in an Elderly Patient

Abstract Background: Solitary plasmacytoma (SP) is a rare plasma cell neoplasm characterized by a localized proliferation of monoclonal plasma cells without systemic involvement. Mandibular localization is exceptional and presents a diagnostic and therapeutic challenge due to the anatomical complexity and risk of progression to multiple myeloma (MM). Objective: This case report aims to explore the effectiveness of exclusive radiotherapy in treating an unresected solitary bone plasmacytoma (SBP) of the mandible in an adult patient. Case Presentation: We report the case of an 80-year-old man with a solitary bone plasmacytoma (SBP) of the mandible, initially presenting as dental mobility and mandibular swelling. Imaging revealed a left parasymphyseal mandibular lesion initially suspected to be osteomyelitis. Histopathological analysis confirmed a mature plasma cell neoplasm. Extensive staging, including bone marrow biopsy and FDG-PET, confirmed the solitary nature of the lesion. Given the patient's refusal of surgery, exclusive conformational radiotherapy was delivered to a total dose of 46 Gy in 23 fractions, with good tolerance. Post-treatment evaluation showed significant tumor regression and stable clinical condition. Discussion: Mandibular plasmacytomas are extremely rare and may mimic inflammatory or infectious lesions. Diagnosis relies on imaging, histopathology, and exclusion of systemic disease. Radiotherapy remains the cornerstone of treatment, achieving high local control rates. However, long-term follow-up is crucial due to the significant risk of progression to MM. Conclusion: This case highlights the effectiveness of exclusive radiotherapy in the management of solitary mandibular plasmacytoma and underscores the importance of thorough diagnostic workup and multidisciplinary evaluation. Further studies are needed to optimize therapeutic strategies in such rare and complex presentations.