PITUITARY-ADENOMA AS AN UNSUSPECTED CLIVAL TUMOR

Pituitary adenomas are common tumors that account for about 10% of int racranial neoplasms. Most arise from the adenohypophysis and are confi ned to the region of the sella turcica. Other sites may be involved as a result of extension, infiltration, or ectopic location. However, po sterior extension or ectopic involvement of the clivus of the sphenoid and occipital bones is rare. Seven patients with destructive clival m asses were referred to our institution with presumptive diagnoses of c hordomas. In all cases, histologic workup revealed pituitary adenomas. Because they represent a subset of adenomas, the histologic features of the tumors were studied, and the clinical histories of the patients were reviewed. Five of the patients were men, aged 31 to 67 years, an d two were women, aged 55 and 67 years. Four patients had extremely hi gh plasma concentrations of prolactin (8,132-22,424 ng/ml, nl < 15). F our tumors resembled usual sellar adenomas; however, three exhibited n uclear pleomorphism, mitotic figures, and other morphologic features, suggesting alternate diagnoses. Three required immunoperoxidase stains in addition to those for pituitary hormones, and three required elect ron microscopy for diagnosis. Destructive invasion of the clivus by pi tuitary adenomas is rare, and anaplastic features of some of the tumor s may lead to difficult diagnoses.