Multiple myeloma presenting as a giant osteolytic skull mass: Surgical challenges and pitfalls - A case report.

Background: Osteolytic skull lesions can result from a broad spectrum of benign and malignant conditions, with multiple myeloma (MM) being a significant malignant cause in adults. Although skull involvement is relatively common in MM, giant exophytic lesions with extensive calvarial destruction and intracranial extension are exceedingly rare and pose diagnostic and therapeutic challenges. Case Description: A 48-year-old male presented with progressive right-sided weakness and a visibly enlarging skull mass. Computed tomography (CT) brain scan revealed a large, well-defined, enhancing mass measuring 9.02 × 7.29 × 6.5 cm, located extra-axially, causing significant compression of the left cerebral hemisphere and ventricle. Magnetic resonance imaging confirmed a large, destructive left frontoparietal lesion with marked bone erosion, and mass effect on the underlying cerebrum. The patient underwent preoperative embolization, followed by surgical resection of the tumor with wide margins and decompression, including removal of the involved skull. Histopathological and immunohistochemical analyses confirmed a high-grade malignant plasma cell neoplasm consistent with MM. Subsequent positron emission tomography-CT and bone marrow biopsy demonstrated systemic disease. The hematology team took over care of the patient for definitive systemic therapy. Conclusion: Giant exophytic skull lesions due to MM are rare and often mimic other neoplastic conditions. This case underscores the importance of early recognition, thorough diagnostic workup, and a multidisciplinary treatment approach. Radical neurosurgical resection combined with systemic oncological therapy is essential to optimize patient outcomes in such uncommon but aggressive presentations.