Learn The BasicsEndometrial cancer (EC) can be classified into different types based on several criteria.
Traditional classification
The traditional classification divides EC into two types based on whether the cancer is estrogen-dependent.
According to this, type 1 EC is the most common, constituting 80% of all cases, and is dependent on estrogen for growth. This type of EC is usually not very aggressive and does not spread to other parts of the body quickly. It is known as an endometrioid adenocarcioma, meaning that the cancer originated from gland cells and resembles normal endometrial glands of the uterus.
Type 2 EC, on the other hand, does not depend on estrogen for growth and has a poorer prognosis compared to type 1 EC. Type 2 EC includes rarer histologic subtypes like clear cell, serous, carcinosarcoma and undifferentiated/dedifferentiated.
WHO classification
The World Health Organization (WHO) classifies EC based on histological appearance. According to this, there are seven types of EC. These are endometrioid carcinoma, serous carcinoma, clear cell carcinoma, undifferentiated or dedifferentiated carcinoma, mixed carcinoma, carcinosarcoma and other rare endometrial carcinomas.
Endometrioid carcinoma can also be divided into subgroups, which are adenocarcinoma with squamous differentiation, secretory adenocarcinoma, ciliated carcinoma, villoglandular, and adenocarcinoma not otherwise specified.
Classification based on grade
EC can also be classified based on the percentage of cancer cells. According to this, there are three grades of EC.
Grade 1 EC has 5% or less cancer cells in a tumor sample. In grade 2 EC, there are anywhere between 6% and 50% cancer cells. In grade 3 EC, cancer cells constitute more than 50% of all cells in a sample.
Grade 3 EC tends to be more aggressive, i.e., grow faster and spread rapidly to other parts of the body, compared to grade 1 and grade 2 EC.
Classification based on stage
EC can be classified into different stages based on the size of the tumor, whether or not it has spread to lymph nodes, and whether or not it has spread to other parts of the body. This is sometimes referred to as the TNM system.
According to this, stage 1 EC is only present inside the uterus or womb.
Stage 2 EC has spread to the connective tissue of the cervix, but is still inside the uterus and no cancer cells are present in the lymph nodes.
In stage 3 EC, cancer cells have spread outside the uterus but have not reached the rectum or bladder. They may have spread to nearby lymph nodes, the surface of the uterus, the ovaries, the vagina or other tissues in the pelvis.
In stage 4 EC, cancer cells have spread to the inner lining of the rectum, the bladder, liver and even other distant organs like the lungs and peripheral lymph nodes.
Molecular classification
EC can also be classified based on the type of mutation that it is associated with. According to this classification, there are 4 types of EC. These are DNA polymerase epsilon (POLE)-mutated, mismatch repair-deficient, P53 abnormal and no specific molecular profile.
This classification system can help identify the likelihood of the cancer recurring following treatment and identify the best treatment option that is most likely to be effective.
The Cancer Genome Atlas (TCGA) Research Network described four molecular subgroups of EC. These are POLE ultramutated, microsatellite instability hypermutated, copy-number low and copy-number high.