It is sometimes difficult to determine whether endometrioid carcinoma has invaded the myometrium. The main criteria are the presence of a pro-fibrotic response, an inflammatory response, direct contact between the cancerous glands and the myometrium in a flattening pattern, and the need to exclude adenomyosis involvement. If there is visible endometrial mesenchyme (or normal glands) between the cancerous glands and the myometrium, the cancer is considered to be confined to the endometrium. However, CD10 staining is not helpful. Tissues surrounding the nest of invasive endometrial adenocarcinoma and smooth muscle will also be positive for CD10 staining. Lu Chaohui, Department of Pathology, Peking Union Medical College Hospital For clinical treatment, the depth of infiltration mainly involves whether lymph node dissection is needed, and usually stage 1,2 T1a carcinoma does not require lymph node dissection. In the old version (1988) of FIGO staging, stage I (tumor limited to uterine body) is divided into Ia, Ib and Ic. Ia refers to tumor limited to endometrium, Ib invades myometrium and is less than 50% of depth, and Ic is greater than or equal to 50% of depth, while the new version of TNM and FIGO staging both abolish Ic, only Ia and Ib, in which Ia refers to tumor limited to endometrium or less than 50% of myometrium. Therefore, if the depth of cancer infiltration is less than 1/2 of the myometrium, it is not necessary to bother too much about whether the cancer has just invaded the myometrium. In the United States, some of the more meticulous specialty hospitals also choose lymph node dissection for high-grade tumors, such as grade 3 endometrioid carcinoma and type II carcinoma, which infiltrate to a depth of 1/3 of the myometrium.