Fast Five Quiz: How Much Do You Know About Diagnosing and Treating Metastatic Colorectal Cancer?

Elwyn C. Cabebe, MD


July 02, 2019

In 2017, the AJCC introduced stage M1c to the eighth edition of its TNM classification and staging manual. Defined as "metastasis to the peritoneal surface alone or with other site or organ metastases," stage M1c represents the poor prognosis of peritoneal carcinomatosis.

The complete AJCC TNM classification and staging for distant metastatic CRC is as follows:

  • M0: No distant metastasis by imaging or other studies, no evidence of tumor in distant sites or organs (this category is not assigned by pathologists)

  • M1: Metastasis to one or more distant sites or organs or peritoneal metastasis

  • M1a: Metastasis confined to one organ or site (eg, liver, lung, ovary, nonregional node) without peritoneal metastasis

  • M1b: Metastasis to two or more sites or organs without peritoneal metastasis

  • M1c: Metastasis to the peritoneal surface alone or with other site or organ metastases

Of note, the AJCC TNM classification does not classify T4b tumors as metastatic, but rather as tumors that directly invade or adhere to other organ structures.

For more information on the staging of colon cancer, read here.


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