From: Colon Cancer Treatment (PDQ®)
PDQ Cancer Information Summaries [Internet].
Bethesda (MD): National Cancer Institute (US); 2002-.
NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.
Table 5. Definitions of TNM Stages IVA, IVB, and IVCa
| Stage | TNMb,c | Definition | Illustration |
|---|---|---|---|
| IVA | Any T, Any N, M1a | TX = Primary tumor cannot be assessed. |
 |
| T0 = No evidence of primary tumor. | |||
| Tis = Carcinoma in situ, intramucosal carcinoma (involvement of lamina propria with no extension through muscularis mucosae). | |||
| T1 = Tumor invades the submucosa (through the muscularis mucosa but not into the muscularis propria). | |||
| T2 = Tumor invades the muscularis propria. | |||
| T3 = Tumor invades through the muscularis propria into pericolorectal tissues. | |||
| T4 = Tumor invades the visceral peritoneum or invades or adheres to adjacent organ or structure. | |||
| –T4a = Tumor invades through the visceral peritoneum (including gross perforation of the bowel through tumor and continuous invasion of tumor through areas of inflammation to the surface of the visceral peritoneum). | |||
| –T4b = Tumor directly invades or adheres to adjacent organs or structures. | |||
| NX = Regional lymph nodes cannot be assessed. | |||
| N0 = No regional lymph node metastasis. | |||
| N1 = One to three regional lymph nodes are positive (tumor in lymph nodes measuring ≥0.2 mm), or any number of tumor deposits are present and all identifiable lymph nodes are negative. | |||
| –N1a = One regional lymph node is positive. | |||
| –N1b = Two or three regional lymph nodes are positive. | |||
| –N1c = No regional lymph nodes are positive, but there are tumor deposits in the subserosa, mesentery, or nonperitonealized pericolic, or perirectal/mesorectal tissues. | |||
| N2 = Four or more regional nodes are positive. | |||
| –N2a = Four to six regional lymph nodes are positive. | |||
| –N2b = Seven or more regional lymph nodes are positive. | |||
| M1a = Metastasis to one site or organ is identified without peritoneal metastasis. | |||
| IVB | Any T, Any N, M1b | Any T = See T descriptions above in Any T, Any N, M1a TNM stage group. | |
| Any N = See N descriptions above in Any T, Any N1, M1a TNM stage group. | |||
| M1b = Metastasis to two or more sites or organs is identified without peritoneal metastasis. | |||
| IVC | Any T, Any N, M1c | Any T = See T descriptions above in Any T, Any N, M1a TNM stage group. | |
| Any N = See N descriptions above in Any T, Any N1, M1a TNM stage group. | |||
| M1c = Metastasis to the peritoneal surface is identified alone or with other site or organ metastases. |
T = primary tumor; N = regional lymph nodes; M = distant metastasis.
aReprinted with permission from AJCC: Colon and rectum. In: Amin MB, Edge SB, Greene FL, et al., eds.: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer, 2017, pp 251–74.
bDirect invasion in T4 includes invasion of other organs or other segments of the colorectum as a result of direct extension through the serosa, as confirmed on microscopic examination (e.g., invasion of the sigmoid colon by a carcinoma of the cecum) or, for cancers in a retroperitoneal or subperitoneal location, direct invasion of other organs or structures by virtue of extension beyond the muscularis propria (i.e., respectively, a tumor on the posterior wall of the descending colon invading the left kidney or lateral abdominal wall; or a mid or distal rectal cancer with invasion of prostate, seminal vesicles, cervix, or vagina).
cTumor that is adherent to other organs or structures, grossly, is classified cT4b. However, if no tumor is present in the adhesion, microscopically, the classification should be pT1-4a depending on the anatomical depth of wall invasion. The V and L classification should be used to identify the presence or absence of vascular or lymphatic invasion whereas the PN prognostic factor should be used for perineural invasion.