Pituitary tumors are most commonly classified according to morphology and function: i. According to morphology, pituitary tumors can be classified into microadenomas, macroadenomas, and macroadenomas. ii. Microadenomas are pituitary tumors with a diameter of ≤1cm, macroadenomas are pituitary tumors with a diameter of >1cm, and macroadenomas are adenomas with a diameter of ≥4cm. Second, according to the level of hormones affected by the pituitary gland, functional pituitary tumors can be classified into different cases, such as ACTH tumors, TSH tumors, growth hormone tumors, prolactin tumors and so on. In addition to these two classification methods, there are also some classification methods according to the relationship with the surrounding tissues, and the most commonly used clinical method is Hardy-Wilson’s grading method, which classifies pituitary tumors into five grades.