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AdenoCA of Colon : TNM Staging

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Pathologic stage is the single most important predictor of clinical behavior in colorectal carcinoma. The TNM staging system is the most widely used system in North America. The tumor is classified based on the depth of invasion.

Tx: Primary tumor cannot be assessed.
T0: No evidence of primary tumor.
Tis: It includes high-grade dysplasia and intramucosal carcinoma. The tumor is confined to the mucosa. The cancer cells invade into the lamina propria and may involve but not penetrate through muscularis mucosa. The risk of metastasis is negligible.
T1: The tumor has invaded through muscularis mucosae into the submucosa. Muscularis propria is spared.
T2: Tumor penetrates through submucosa into but not beyond muscularis propria.
T3: Tumor penetrates through muscularis propria to involve subserosal adipose tissue or non-peritonealized pericolic or perirectal soft tissues.
T4: Tumor involves the serosal surface (visceral peritoneum) or directly invades adjacent organs/structures. 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.

T4 tumors have a higher risk of peritoneal relapse. The significance of tumors that are less than 1mm from the serosal surface and accompanied by a serosal reaction is unclear. Multiple sections should be examined to definitively rule out serosal involvement.

The image shows serosal involvement with puckering (Stage T4a) in a case of colon cancer arising at the splenic flexure. Image courtesy of: Jian-Hua Qiao, MD, Los Angeles, California, USA. Used with permission.

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