Pituitary tumors: Update on histopathological diagnosis

The majority of pituitary tumors are benign noninvasive adenomas. However, aggressive behavior is not uncommon, and the tumor often extends beyond the sellar region. Recently, the classification of pituitary adenoma (PA) in relation to aggressive lesions has been amended. The new edition of the World Health Organization recommends that major changes be made to the current classification of tumors of the adenohypophysis. It is thus the purpose of this review to provide the reader with a general overview of the changes that have been suggested. This includes a novel approach to classifying pituitary neuroendocrine tumors, the revision of the histological grading (in which the term “atypical” PA is discontinued), the redefinition of old entities and the introduction of new ones.