Pituitary adenomas - practical approach to the diagnosis and the changes in the 2017 WHO classification

The histopathological diagnosis of sellar tumors is a difficult area of the diagnostic surgical pathology. The most common sellar tumor is a pituitary adenoma. The histomorphology of pituitary adenomas is very heterogeneous, and in the sellar area, we can encounter practically any other tumor known from human pathology, either primary or secondary. Exact histopathological classification requires many immunohistochemical antibodies: pituitary hormones, pituitary transcription factors, and several other antibodies. At present, electron microscopy is no longer necessary for the routine diagnosis of the pituitary gland adenomas. The important aspect of the precise classification is to screen pituitary adenomas for aggressive histological types. The latest edition of the WHO classification of tumours of endocrine organs, published in 2017, involves several changes in the chapter of pituitary adenomas, including the abolition of the concept of atypical adenoma. In the short review, we discuss the practical approach to the diagnosis and the changes in the latest WHO classification of pituitary adenomas from 2017.