Pathological correlates of pituitary adenomas presenting with apoplexy.

Pituitary adenomas presenting de novo with apoplectic symptoms are uncommon. Several series on pituitary adenomas with apoplexy have been reported but have emphasized clinical aspects, incidence, or radiographic appearance by computed tomography (CT) scan. We reviewed our 13 years' experience, focusing on pathological appearance. We identified 15 patients with pituitary adenomas whose first presentation to our institution was with apoplexy. By combining histological and intraoperative findings with more sensitive magnetic resonance imaging (MRI) scans, we were able to attribute 5 of 15 cases to bland infarction, five cases to hemorrhagic infarction, four cases to pure clot, and one to a remote hemorrhagic infarction leaving extensive residual fibrosis and hemosiderin. Despite extensive tumor necrosis, reticulin staining still allowed identification of specimens as adenomas. Immunohistochemical staining was informative in 13 of 15 cases and endocrine-inactive, weak gonadotroph and null cell adenomas predominated. Cases with the greatest interval between symptom onset and surgery showed peripheral rim enhancement by MRI. Pathologically, this corresponded to granulation tissue, T cell lymphocytic infiltration, and atrophic pituicytes at the edge of the infarction or hemorrhage. Occasionally this reaction overshadowed the necrotic adenoma and contributed to diagnostic confusion. Our finding of lymphocytic inflammation in pituitary adenomas that have undergone an apoplectic event may suggest at least a modest immune-mediated response to damaged anterior pituitary tissue.