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)