The clinical features of 426 pituitary adenomas were retrospectively analyzed, focusing on the factors that affect the development of pituitary apoplexy. Immunohistochemical analysis was used to define the different hormone types of the tumors and the expression of various immunologic targets, including the pituitary tumor transforming gene, basic fibroblast growth factor-2, matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-1, and proliferating cell nuclear antigen. Of the 426 patients, 83 presented with pituitary apoplexy (19.48%). Among them, 43 patients (43/83, 51.82%) developed apoplexy in the absence of any obvious precipitating factor. Clinical manifestations included headaches (80/83, 96.38%), vision loss (69/83, 83.13%), pituitary function change (51/83, 61.45%), visual field defects (41/83, 49.39%), and nausea and vomiting (34/83, 40.96%). Male patients and patients with functional adenoma had a higher probability of developing apoplexy. Complicated immunological expression patterns were found in adenomas associated with pituitary apoplexy, with adenomas of different hormone types identified.