Tumors of the pituitary gland are frequent intracranial neoplasms. They can affect all ages and show a slight prevalence in females. Clinically, they can present either with signs and symptoms of pituitary hormone hypersecretion, or as space-occupying intracranial masses, with visual defects and headaches as the main symptoms. Rarely, neoplasms in this site may cause hypopituitarism.
Pituitary adenomas represent the most common form of pituitary neoplasms. They are slow-growing, non-metastasizing proliferations of adenohypophyseal cells, although they can show an invasive attitude towards the adjacent bony and vascular structures. The pathogenetic basis of pituitary adenomas does not involve classical oncogenes and tumor suppressor genes, but rather a number of alterations of cell signaling, cell cycle regulators, transcriptional regulators and miRNAs. The diagnosis and classification of pituitary adenomas is largely based on immunohistochemical analyses, with pituitary hormones and specific pituitary-cell lineage transcription factors being the most important markers.
Rare pituitary tumors, including pituitary carcinoma, pituitary blastoma, tumors of the neurohypophysis, neuronal and paraneuronal tumors, mesenchymal and stromal tumors, hematological tumors, germ cell tumors and mixed neuroendocrine–nonneuroendocrine tumors are also discussed in this article.