Endocrine Abstracts

Multiple myeloma is a neoplastic disorder arising from plasma cells in the bone marrow. Plasma cell tumors, plasmacytomas, are uncommon in the brain and occur usually in the leptomeninges with or without parencymal involvement. Extramedullary plasmacytomas are very rarely located in the sella and can be misdiagnosed as a nonfunctioning pituitary adenoma. We report an illustrative case with multiple myeloma who was diagnosed having sellar plasmacytoma resembling a nonfunctioning pituitary adenoma.

A 56-year-old Caucasion woman presented with a history of headache and diplopia. She denied any other neurological symptoms. Her complaints started approximately 6 months ago. She had a mild anemia with a hemoglobin level of 11.1 g/dl (12–14 g/dl). Blood chemistry analyses were normal. Serum prolactin level was slightly elevated at 76.44 ng/ml (1.2–29 ng/ml), but other hypophsial hormones were within normal limits. Magnetic resonance imaging (MRI) of the brain showed a 26×22×31 mm mass destroying the floor of sella and infiltrating the clivus. The presumptive diagnosis was of a nonfunctioning pituitary adenoma and transsphenoidal gross excision was performed. The histological appearance of the specimen was that of a highly cellular neoplasm composed of mature plasma cells with round eccentrically located nuclei. Immuno-cytochemistry showed that all the tumor cells were positive for CD 138 and lambda light chains confirming that this tumor was a plasmacytoma. Post operatively an extensive investigation for myelomatous disease was undertaken including serum and urine protein electrophoresis, a bone survey and a bone marrow biopsy. Serum protein electrophoresis detected a monoclonal gammophathy with IgG kappa type M protein on serum immunfluorescence electrophoresis. Urine was negative for Bence-Jones proteinuria. Beta 2 microglobulin level was 3.2 mg/dl. Bone marrow biopsy showed plasma cell infiltration. The diagnosis of multiple myeloma with involvement of the pituitary gland was made. Subsequently, systemic chemotherapy consisting of melphalan and prednisone was given for 6 cycles. The patient remained in remission for 20 months after the therapy.

In conclusion, although multiple myeloma involving pituitary gland is rare, it must be considered in the differential diagnosis of a nonfunctioning pituitary mass. A hypophysial mass with a normal anterior pituitary hormonal profile should alert the physician for the possibility of a diagnosis other than a chromophobe adenoma.