Metastatic haematological malignancy presenting as a sellar mass

A man in his 60s with a history of multiple myeloma diagnosed 6 months previously was referred with a diagnosis of a sellar mass. He reported a 3-month history of headaches associated with double vision which appeared to improve with corticosteroid treatment. An MRI scan revealed a 3.7 cm × 3 cm × 2.6 cm sellar mass with erosion into the sphenoid sinus and extending to the right cavernous sinus. Pituitary function tests were normal apart from hypogonadotrophic hypogonadism. A diagnosis of plasmacytoma was considered and so transphenoidal biopsy of the sellar lesion was organised, which revealed sheets of mature appearing plasma cells, staining exclusively for κ-light chain immunoglobulins. He was to be started on chemotherapy for the myeloma and radiotherapy for the plasmacytoma. The patient's clinical course was complicated by community-acquired pneumonia and renal failure resulting in his death a month after the diagnosis of plasmacytoma.