Colorectal Carcinoma

Few investigators have applied imaging methods to staging of suprarectal colonic carcinomas.25-28 The vast majority of clinical studies have been directed to the di agnosis, staging, and management of carcinomas of the rectum.

The TNM classification for colorectal cancer (Table 5-3 and Fig. 5-2) of the American Joint Committee on Cancer (AJCC) and the Union Internationale Contra le Cancer (UICC)1,3 is compatible with the Dukes classification.

The most important independent pathologic factor for survival or recurrence after potentially curative surgery is the depth of the cancer's penetration through the bowel wall and the presence and number of positive

29-31

lymph nodes. The status of the cancer in relation to the muscularis propria demarcates T2 and T3 tumors. The classification stratifies regional nodal involvement by one to three compared with four or more positive nodes, a dichotomy of prognostic significance, with a 5-year survival rate of 66% and 37%, respectively.32

Table 5-3. TNM Clinical Classification System for Staging Colorectal Cancers

Primary tumor (T)

TX Primary tumor cannot be assessed TO No evidence of primary tumor

Tis Carcinoma in situ: confined within the glandular basement membrane (intraepithelial) or lamina propria (intramucosal) Tt Tumor invades the sub mucosa T2 Tumor invades the muscularis propria

T3 Tumor invades through the muscularis propria into the sub serosa or into nonperitonealized pericolic or perirectal tissues T4 Tumor direcdy invades other organs or structures and/or perforates the visceral peritoneum

Regional lymph nodes (N)

NX Regional lymph nodes cannot be assessed

NO No regional lymph node metastasis

N1 Metastasis in 1—3 pericolic or perirectal lumph nodes

N2 Metastasis in pericolic or perirectal lymph nodes

Distant metastasis (M)

MX Presence of distant metastasis cannot be assessed MO No distant metastasis Ml Distant metastasis

Stage grouping

Distant metastasis (M)

MX Presence of distant metastasis cannot be assessed MO No distant metastasis Ml Distant metastasis

Stage grouping

AJCC/UICC

Stage 0

Tis

NO

MO

Stage i

T1

NO

MO

T2

NO

MO

Stage II

T3

NO

MO

T4

NO

MO

Stage III

Any T

Nl

MO

Any T

N2

MO

Stage IV

Any T

Any N

Ml

aThe Dukes classifications do not encompass all three prognostic factors in one staging system. Dukes B is a composite of better (T3, NO, MO) and worse (T4, NO, MO) prognostic groups, as is Dukes C (any T, Nl, MO and any T, N2, MO).

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