An unusual sellar mass--solitary plasmacytoma.

Objective: To describe a case of solitary intrasellar plasmacytoma in a patient with a preoperative diagnosis of a nonfunctioning pituitary adenoma.

Methods: A case of a solitary intrasellar plasmacytoma is presented, in which the clinical and laboratory findings are detailed and the response to treatment is discussed. Pertinent reports from the literature are reviewed.

Results: A 53-year-old woman came to the neurology clinic with complaints of frontal headaches and intermittent blurry vision. Physical examination showed no remarkable findings. Computed tomography revealed an enhancing sellar and suprasellar mass, with extension into the sphenoid and cavernous sinuses. The patient had a preoperative diagnosis of a clinically nonfunctioning pituitary adenoma and underwent transsphenoidal resection. The biopsy specimen was heavily infiltrated with abnormal plasma cells, which stained exclusively for lambda light chain immunoglobulins. An extensive investigation failed to show evidence of multiple myeloma. In view of these findings, the diagnosis of solitary extramedullary plasmacytoma was made. Postoperatively, the patient received radiotherapy to the pituitary and has remained free of disease for 7 years. Review of the world literature disclosed only 17 previous reports of patients in whom a solitary plasmacytoma or multiple myeloma first appeared as a sellar mass. In each case, the plasmacytoma mimicked a clinically nonfunctioning pituitary adenoma.

Conclusion: Parasellar plasmacytomas are often mistaken for a nonfunctioning pituitary adenoma. The diagnosis is difficult to make in the absence of overt systemic myeloma. Nevertheless, normal pituitary function associated with severe destruction of the pituitary fossa, cranial neuropathies, and diabetes insipidus are clues that the primary lesion is outside the pituitary gland itself. The current patient is unique in terms of prolonged survival in the absence of systemic myeloma. Perhaps those patients with progression of disease did not have extramedullary tumors because such lesions rarely progress to overt myelomatous disease.