Figure 2 : CBCT showing bone damage with this mitted bone appearance
However, biopsy revealed a monotypic lambda plasma cell infiltration consistent with a plasmacytoma. Ki67 proliferation index shows a proliferation index of 20%. Complementary investigations showed no systemic involvement, leading to the definitive diagnosis of bone solitary mandibular plasmacytoma. The PET scan shows intense hypermetabolism of the lesion, with no other systemic damage. Next-generation high-throughput sequencing shows no anomalies
Management included five sessions of radiotherapy and chemotherapy with daratumumab, dexamethasone, and lenalidomide, as decided by the oncology team.
For the past 6 months, the lesion has remained asymptomatic, reduced in size at bone level. However, the patient presents with mucositis due to radiotherapy. Biological tests remain normal.
DISCUSSION
Solitary plasmacytoma of bone accounts for 5% of plasma cell tumors. Solitary plasmacytoma has a predisposition for the red marrow-containing axial skeleton and is most frequently seen in the thoracic vertebrae, followed by the ribs, sternum, clavicle, or scapula. Mandibular localization remains rare.(1) Radiotherapy remains the treatment of choice, but radiation-related drawbacks are fairly frequent, which is why chemotherapy is also of interest. The risk of progression to multiple myeloma despite irradiation is 50% at 5 years. Regular and rigorous follow-up is therefore vital. (2,3)