TNM Staging | AJCC 2017
The TNM staging system anatomically classifies malignancies based on the extent of the primary tumour, regional lymph node involvement, and distant metastases. Staging helps physicians decide eligibility for clinical trials, define a patient's prognosis, and determine best treatment options.
The American Joint Committee on Cancer (AJCC) publishes the AJCC Cancer Staging Manual every 6-8 years. This tool is based on the 8th edition (2017) which represents the most up to date TNM staging guide.
1. Primary Tumour (T)
* Direct 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 (for example, 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 (ie, respectively, a tumour 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).
**Tumour that is adherent to other organs or structures, grossly, is classified cT4b. However, if no tumour 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.