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

Background: Solitary plasmacytoma (SP) is a rare plasma cell tumor causing localized monoclonal plasma cell proliferation without systemic disease. Mandibular cases present diagnostic and management difficulties due to both anatomical complexity and the risk of progression to multiple myeloma (MM). This report evaluates the clinical outcome of exclusive radiotherapy in 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. He first presented with 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 lesion’s solitary nature. The patient refused 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 a stable clinical condition. Conclusion: This case demonstrates that exclusive radiotherapy can achieve significant tumor regression and clinical stability in a solitary mandibular plasmacytoma. Comprehensive diagnostic evaluation and multidisciplinary management are crucial for such rare clinical situations. Further research is needed to refine strategies for these complex cases.