Intrasellar plasmacytoma presenting as a non-functional invasive pituitary macro-adenoma: case report & literature review.

We report an uncommon case of an intrasellar plasmacytoma presenting as a non-functional invasive pituitary macro-adenoma as the first manifestation of multiple myeloma. A 57 year old woman was referred to our department with a presumed diagnosis of a non-functioning pituitary macro-adenoma. She reported a 3 month history of headaches and a 2 week history of sudden onset of right facial numbness. Preoperative endocrine evaluation was remarkable only for a modestly elevated serum prolactin. A magnetic resonance imaging (MRI) scan revealed 3.6 x 5 x 4 cm enhancing homogeneous intrasellar mass with extension into the sphenoid and cavernous sinuses bilaterally; the optic chiasm was not displaced. She underwent transphenoidal surgery of the sellar lesion. The surgical specimen was heavily infiltrated with abnormal plasma cells, which stained almost exclusively for Kappa light chain immunoglobulins. An extensive investigation was undertaken to look for occult myelomatous disease. A diagnosis of multiple myeloma was made 1 month later based on a combination of clinical, pathological and radiologic features. She underwent radiation therapy directed towards the residual sellar tumor, followed by chemotherapy and autologous stem cell transplantation. Review of the world literature revealed only 22 previous reports of patients in whom a solitary plasmacytoma or multiple myeloma first presented as a sellar mass; in all cases mimicking clinically and radiologically a non-functioning invasive pituitary adenoma however with additional cranial nerve involvement. Intrasellar plasma cell tumors are rare tumors which may mimic non-functioning invasive pituitary tumors. The diagnosis should be suspected in patients with well preserved anterior pituitary function and cranial nerve neuropathies in the presence of significant sellar destruction.