Rectal cancer staging is based on the TNM system. "T" refers to the primary tumor, and its stage depends on which layer of the bowel wall the tumor has invaded. "N" is based on whether there are lymph node metastases and the number of lymph nodes involved. "M" indicates whether there are metastases to distant organs. Staging is determined according to the TNM situation, where Stage I is the earliest and Stage IV is the latest. Stage III indicates lymph node metastasis without distant organ metastases, such as to the liver or lungs. In such cases, irrespective of whether T is T1 to T4, if there is lymph node involvement without distant organ metastasis, it is staged as Stage III.