Dural-Based Plasmacytoma Presenting As the Initial Sign of Multiple Myeloma

In multiple myeloma (MM), intracranial involvement is rare, particularly in cases of dural involvement. Cranial plasmacytoma can be seen in MM and may occasionally present as a solitary lesion. On MRI, dural plasmacytomas can mimic other extra-axial masses such as meningiomas, metastases, lymphomas, or sarcomas of the dura mater. A 66-year-old woman presented with a right occipital swelling identified on an external MRI scan, which was accompanied by a headache. The MRI suggested MM or parieto-occipital intraosseous meningioma. The patient was advised to undergo a follow-up MRI, which she did not attend. Three months later, a head CT scan revealed that the mass had regressed spontaneously, and she remained asymptomatic. For that reason, she declined treatment. Five months later, the patient returned with left-sided hemiparesis. Follow-up imaging showed significant growth of the tumor. After tumor extraction, histopathological analysis with immunohistochemistry revealed a plasma cell neoplasm with lambda light chain. Prior to making treatment decisions, it is crucial to conduct a thorough systemic evaluation and preoperative workup for MM when plasmacytoma is considered in the differential diagnosis.