Adenocarcinoma in situ is a pre-infiltrative lesion of cancer and is a category of carcinoma in situ. Adenocarcinoma is a malignant tumor originated from glandular epithelium. 1. Adenocarcinoma in situ: it is pre-infiltrating lesion of carcinoma, with low malignant degree, high surgical cure rate, and no recurrence and metastasis after regular postoperative review. 2. Adenocarcinoma: it is a malignant tumor originated from glandular epithelium, which can be seen under the microscope with different sizes, different morphology and irregular arrangement. It is often found in breast, prostate, uterus, ovary and other organs, and part of it can be cured by surgery. Adenocarcinoma in situ and adenocarcinoma should be comprehensively diagnosed by professional doctors with the combination of medical history, symptoms, signs and relevant examinations, and early detection, early diagnosis and early treatment should be achieved to improve the cure rate of the disease.