A 74-year old male presented with a left sixth cranial nerve palsy and three month history of headache and diplopia but no weight loss, or symptoms of anterior pituitary insufficiency or diabetes insipidus. Past medical history included Crohn’s disease, hypertension, ischaemic heart disease and permanent pace maker for symptomatic bradycardia. Left cranial nerve six palsy with no visual field defect was evident on examination. Pre-operative pituitary function and blood chemistry was within normal limits. An enhancing sellar lesion with suprasellar extension and skull base involvement measuring 28 x 34 x 35 mm was evident on neuroimaging. Pituitary histopathology reported sheets of atypical plasma cells, positive for CD79a, CD138 with light chain restriction, consistent with plasmacytoma. Extensive investigation did not reveal underlying multiple myeloma and he commenced treatment with radiation to the sellar region for the isolated sellar plasmacytoma. Follow-up revealed the eventual development of systemic multiple myeloma, 13 months after his initial presentation.
Isolated plasmacytoma presenting as a pituitary mass is rare. Headache, diplopia and visual field defects are the most frequent presenting symptoms. Cranial nerve palsy is common, mainly affecting the abducens nerve. Most patients have intact anterior pituitary function and imaging typically portrays an invasive mass. Radiotherapy is usually the initial treatment, with chemotherapy or autologous stem cell transplant utilised for systemic multiple myeloma. Solitary plasmacytomas have been reported to progress to multiple myeloma in 30-60% of cases.
Sellar plasmacytomas are rare and are often mistaken for non-functioning pituitary adenomas. An aggressive, destructive sellar mass with cranial nerve palsy but minimally disturbed anterior pituitary function should raise suspicion of a plasmacytoma. As treatment and prognosis differ, it is important to detect underlying multiple myeloma in patients presenting with sellar plasmacytoma.