Pituitary adenoma is a common benign intracranial tumor, accounting for approximately 10-15% of intracranial tumors and ranking second among benign intracranial starting tumors. This tumor originates from pituitary gland cells. The incidence in the population is 1-7/100,000. The disease is more common in young adults and only 10% of children.
Pituitary adenomas are currently divided into two categories: hormone-secreting and non-functional. The main types of hormone-secreting adenomas are: (1) pituitary lactogenic adenoma; (2) pituitary growth hormone adenoma; (3) pituitary adrenocorticotropic hormone (ACTH) adenoma; and (4) pituitary thyroid adenoma.
Pathology classifies pituitary adenomas into 3 categories based on the size of the tumor: microadenomas <1 cm, macroadenomas ≥1 cm, and giant adenomas ≥3 cm. Gross specimen: pituitary tumors are often grayish red or purplish red, soft in texture, and some are ropy. Microscopic examination: classification according to tumor cell staining: (1) suspicious cell adenoma; (2) eosinophilic adenoma; (3) basophilic adenoma. Immunohistochemical classification: (1) PRL adenoma; (2) GH adenoma; (3) ACTH adenoma; (4) TSH adenoma. Pituitary adenomas have a border but no envelope. Some pituitary adenomas infiltrate into adjacent normal pituitary tissue. In general, adenoma cells are distinguished from normal pituitary cells by their uniform morphology, oval shape, round nuclei, distinct nucleoli, abundant chromatin, loss of the normal short cord arrangement, and changes in the basement membrane of the cells.