Plasmacytoma: an unusual cause of a pituitary mass lesion. A case report and a review of the literature.

A sixty six year old female presented with headache and decreased hearing. Clinical examination confirmed the presence of impaired hearing on the left side. Visual fields were full to confrontation and corrected visual acuity was normal. CT scan of brain revealed a pituitary mass. Preoperative anterior pituitary function was normal. Transsphenoidal decompression was performed, and histology was that of a plasmacytoma. Post operative pituitary function was normal. The patient had no symptoms or signs of multiple myeloma and subsequent investigations revealed no evidence of the disease. One year after diagnosis a course of radiotherapy was administered for local tumour recurrence. During seven years of follow-up, no evidence of multiple myeloma has emerged. Only thirteen similar cases have been described. Four of these had evidence of multiple myeloma at presentation and six progressed to it during follow-up. In twelve patients cranial nerve deficits were recorded. In any cases where it was documented, preoperative anterior pituitary function was normal. In a number of cases histology was reported initially as being that of a non-functioning adenoma, the true diagnosis being discovered, either by electron microscopy findings or after the development of multiple myeloma. Plasma cell tumours of the pituitary area are rare and can present with symptoms and signs indistinguishable from non-functioning adenoma. Atypical symptoms such as cranial nerve involvement or unexpected preservation of anterior pituitary function should arouse suspicion.