(CSEMP046) SUPRASELLAR MASS: A RARE CASE OF PRIMARY CENTRAL NERVOUS SYSTEM MARGINAL ZONE LYMPHOMA

Abstract:

Introduction: Sellar and suprasellar masses are found incidentally on 4-20% of Cranial CTs. Pituitary adenomas, craniopharyngiomas, aneurysms, astrocytomas and meningiomas are the most common lesions in the sellar area, accounting for approximately 80% of cases. Primary central nervous system lymphomas constitute fewer than 5% of suprasellar masses, with only 2 prior cases of CNS Marginal Zone Lymphoma being described in the literature.

Case Description: 39-year-old male with no significant medical, surgical or family history except for corrective eye surgery presented with acute bilateral proptosis, headache and bilateral temporal hemianopsia. Slit lamp exam was unremarkable. CT orbit showed an enhancing suprasellar mass that was iso-intense to the brain parenchyma. MRI Sella Turcica reported a large mass (2.2 x 2.5 x 3.0 cm) in the tuberculum sellae with extension into the right cavernous sinus, encasement of the right internal carotid artery, and mass effect on the optic chiasm and the right optic nerve. Pituitary panel showed no hormone excess or deficiency. Serum protein electrophoresis detected a small monoclonal peak [2 g/dl] in the gamma region, confirmed to be IgG lambda light chain by serum immunofixation. Patient underwent transcranial resection of the suprasellar mass, followed by radiation therapy. Pathology revealed B-cell lymphoma with marked plasma cells, suggestive of lymphoplasmacytic lymphoma (LPL) or marginal zone lymphoma (MZL) with marked plasmacytic differentiation. Immunohistochemistry underscored the large plasmacytic component, positive for CD138 and MUM1, showing lambda light chain restriction (by ISH). At three-year follow-up, patient has not had any recurrence, with marked improvement in his vision and unchanged pituitary hormone function.

Discussion:
Pituitary adenoma is by far the most common sellar/suprasellar tumor type. Typical MRI findings in primary CNS MZL are mass lesions that are iso- to hypointense on T1- and T2-weighted images. Pituitary adenomas, especially when larger than 1cm, can have a heterogeneous appearance on MRI depending on hemorrhagic, cystic, and necrotic components. CNS MZL, similar to other primary CNS lymphomas appear homogeneous. Hematological studies intended to uncover monoclonal gammopathy are not in the practice guidelines for the evaluation of pituitary incidentalomas. However, if positive, they lend strong support for primary CNS lymphoma as the underlying etiology. Thus, although primary CNS lymphoma may be indistinguishable from pituitary adenoma on imaging, it should be considered in the differential in the evaluation of an invasive sellar mass that is iso- to hypointense on T2-weighted MRI image.