Salivary Gland-Like Tumors of the Sellar Region

Abstract

Herein we present a group of rare tumors of the sella region that have not been previously recognized. Although clinically and radiographically the tumors resemble nonfunctioning pituitary adenomas, their histologic, immunohistochemical, and ultrastructural features differ and indicate a salivary gland origin. The lesions cover a morphologic spectrum that includes cellular pleomorphic adenoma, monomorphic adenoma, oncocytoma, and low-grade adenocarcinoma of the salivary gland. All tumors except the oncocytoma were immunoreactive for cytokeratin and were negative for pituitary hormones and synaptophysin. Ultrastructural characteristics in the cases examined include hypodense stromal material, basal lamina, and tonofilament bundles. The single oncocytoma was packed with mitochondria and lacked membrane-bound secretory granules. DNA ploidy based on image analysis and MIB-1 labeling indices showed diversity within this group of tumors, with labeling indices ranging from 0.06% to 15%. The presumed origin of these rare neoplasms is from salivary gland rests related to the normal pituitary gland. Despite their varied morphology, such tumors are easily confused with pituitary adenoma. Although rare, tumors of salivary gland origin should be considered in the differential diagnosis of unusual adenohypophyseal tumors.