The pituitary gland, or hypophysis, and adjacent structures of the sellar region can be affected by a wide range of pathologies leading to endocrine and neurological disorders. These include neoplasms arising from the adenohypophysis, such as pituitary adenomas associated with distinctive endocrine disorders such as acromegaly or Cushing’s disease; cysts or neoplasms derived from remnants of Rathke’s pouch (Rathke’s cleft cyst, craniopharyngioma); tumours of the neurohypophysis and pituitary stalk (pituicytoma, granular cell tumour) and neoplasms of the parasellar bone (chordoma). Further, conditions like lymphocytic or granulomatous hypophysitis may mimic pituitary neoplasms. Here, we provide an overview of the molecular pathogenesis and neuropathological features of these common lesions. For complete coverage of this and related areas of Endocrinology, please visit our free web –book, www.endotext.org.