Colorectal Cancer

Diagnosis and Staging

Doctors rely on many tests to diagnose colorectal cancer. Some tests, such as laboratory studies and imaging studies (for example, computerized tomography [CT]), help doctors assign an initial stage to your cancer. This initial stage is known as the clinical stage because it is based on clinical findings. The final stage is assigned by the pathologist who examines the colon or rectal tumor and lymph nodes that were removed during an operation. This final stage is known as the pathologic stage. The stage provides important information for selecting treatment and for predicting the prognosis (outcome).

Colorectal cancer is classified according to the tumor, node, metastasis (TNM) system developed by the American Joint Committee on Cancer (AJCC). For many cancers, the size and location of the tumor is of critical importance, but for colorectal cancer, how deeply the tumor penetrates the layers of the intestine is the most important feature of the tumor. The T category is used to describe this depth, the N category is used to describe how many nearby lymph nodes are involved (contain cancer cells) and the M category is used to note whether cancer has metastasized (spread to other parts of the body) (Table 1).

Once a colorectal cancer has been classified with the AJCC system, an overall stage is assigned. Five stages (0 to IV) are further subdivided to group tumors that are associated with similar prognoses. This grouping enables doctors to more accurately predict the outcome according to the stage and to recommend the optimal treatment (Table 2).

The stage of your colorectal cancer and other characteristics of the tumor are documented on a pathology report. Other important information about the tumor includes its histologic grade and the status of the surgical margins. The histologic grade indicates how closely the tumor cells resemble healthy cells. Grade 1 cells look similar to healthy cells, and the tumor is likely to grow slowly; in contrast, grade 4 cells look very different from healthy cells, and the tumor is likely to grow quickly. The surgical margin is the area of healthy tissue around where the tumor was located. The pathologist will examine the margin to see if it contains cancer cells. If cancer cells are present in the margins, additional treatment may be needed. Results of testing for genetic mutations in the tumor are also usually noted on the pathology report.

An accurate diagnosis is crucial to receiving appropriate treatment. Do not be afraid to seek a second opinion about your diagnosis and/or treatment plan.

Table 1. American Joint Committee on Cancer (AJCC) System for Classifying Colorectal Cancer

Classification	Definition

Tx	Tumor cannot be evaluated (because of lack of information)
T0	No evidence of primary tumor
Tis	Carcinoma in situ; cancer cells are found only in the mucosa, the first layer or inner lining of the colon or rectum
T1	Tumor has grown into the submucosa, the second layer
T2	Tumor has grown into the muscularis propria, the third layer
T3	Tumor has grown into the subserosa, the deepest layer
T4a T4b	Tumor has grown through the entire wall of the colon The tumor has invaded or is adherent to nearby tissues or organs
Regional (Nearby) Nodes (N)
Nx	Nearby lymph nodes were not evaluated
N0	No cancer cells are found in nearby lymph nodes
N1a N1b N1c	Cancer cells are found in 1 nearby lymph node Cancer cells are found 2 or 3 nearby lymph nodes Cancer cells are found in the subserosa, mesentery (the fatty tissue that contains the lymph nodes and blood vessels) or tissues around the colon or rectum but not in nearby lymph nodes
N2a N2b	Cancer cells are found in 4, 5 or 6 nearby lymph nodes Cancer cells are found in 7 or more nearby lymph nodes
Distant Metastasis (M)
M0	Cancer has not spread beyond nearby lymph nodes
M1a	Cancer is detected in 1 organ or site (for example, the liver, lung, ovary or distant lymph node)
M1b	Cancer is detected in more than 1 organ or site or in the peritoneum (lining of the abdominal cavity)

Table 2. Stage of Colorectal Cancer According to AJCC Classification

Stage	TNM Classification
0	Tis, N0, M0
I	T1 or T2, N0, M0
IIA	T3, N0, M0
IIB	T4a, N0, M0
IIC	T4b, N0, M0
IIIA	T1 or T2, N1(a-c), M0 T1, N2a, M0
IIIB	T3 or T4a, N1(a-c), M0 T2 or T3, N2a, M0 T1 or T2, N2b, M0
IIIC	T4a, N2a, M0 T3 or T4a, N2b, M0 T4b, N1(a-c) or N2, M0
IVA IVB	Any T, Any N, M1a Any T, Any N, M1b

Additional Sources of Information

American Cancer Society: www.cancer.org
How Is Colorectal Cancer Staged?
Getting a Second Opinion
American Society of Clinical Oncology: www.cancer.net
Colorectal Cancer: Staging, with Illustrations
CancerQuest (Winship Cancer Institute, Emory University):www.cancerquest.org
Colon and Rectal Cancer: Pathology Report and Staging
MyBiopsy.org (College of American Pathologists): www.mybiopsy.org
Colon
Oncolink (Abramson Cancer Center of the University of Pennsylvania): www.oncolink.org
Understanding Your Pathology Report: Colon Cancer