A case of incidental multiple Myeloma presenting with pathologically proven large frontal skull plasmacytoma and review of therapeutic targets: Case report


 Introduction: Multiple myeloma and plasmacytoma are both plasma cell malignancies that belong to the family of blood dyscrasias. They are thought to be different entities but can occur simultaneously in some patients.

 Case Report: We present a unique case of a large plasmacytoma heralding the diagnosis of multiple myeloma with a preceding history of trauma which makes this case peculiar as this is an important addition to the limited existing scientific literature. The index patient was largely asymptomatic despite having a massive frontal skull/lobe lesion measuring approximately 8 × 6 cm in size alongside a chest wall mass involving the anterior left 6th rib, and a mildly displaced acute pathological fracture of the left clavicle. A primary diagnosis of multiple myeloma was made following serum protein electrophoresis with pathological confirmation of frontal skull plasmacytoma. After multidisciplinary discussion, radiotherapy was administered for plasmacytoma with complete resolution of the frontal skull mass without the need for resection and chemotherapy for multiple myeloma with daratumumab in combination with lenalidomide-dexamethasone—chosen due to anticipated poor outcome at the time of diagnosis. Autologous stem cell transplantation was subsequently instituted for multiple myeloma with a good outcome to date.

 Conclusion: Solitary plasmacytoma can co-exist with multiple myeloma and the prognosis remains poor in such circumstance. Patients should be followed up closely with yearly imaging—magnetic resonance imaging (MRI)/computed tomography (CT), and positron emission tomography (PET) scans. A pivotal lesson from this case report emphasizes the atypical presentation of plasmacytoma and multiple myeloma with the peculiarity of a prior history of trauma which is believed to be associated with plasma dyscrasias. Over the last decade, novel therapeutic agents such as chimeric antigen receptor T-cell therapy, which is the first approved cell-based therapy for multiple myeloma, antibody-drug conjugates, and a dozen of bi-specific antibodies/immunotherapy have been developed and shows promising outcome in the future, especially for refractory cases of multiple myeloma.
