Giant solitary extradural plasmacytoma of the skull: illustrative case

BACKGROUND: Solitary extradural plasmacytoma of the skull (SEPS) is an extremely rare entity with only 35 cases reported in the English-language literature. SEPS is a rare presentation of plasma cell dyscrasias, accounting for 4% of plasma cell tumors. The diagnosis of solitary plasmacytoma requires exclusion of multiple myeloma (MM) and prompt diagnosis and treatment. OBSERVATIONS: The authors describe the case of a 52-year-old man with SEPS. He presented with a painless, progressive, soft swelling mass in the left parietal region. Magnetic resonance imaging revealed a left frontotemporal extra-axial lesion that involved the ipsilateral orbital apex and posterior ethmoidal cells. Biological studies did not reveal features suggestive of MM. A diagnosis of SEPS was based on microscopic examination and immunohistochemical analysis after surgery. The patient had an excellent recovery and was discharged the day after surgery without neurological deficit. LESSONS: SEPS is a potentially curable disease, and total resection with or without radiotherapy is associated with a good prognosis and long-term recurrence-free survival. Distinction between SEPS and MM is of paramount importance because the prognosis and treatment differ.