TNM Definitions
AJCC Stage Groupings

The treatment sections of this summary are organized according to histopathologic type rather than stage.

The American Joint Committee on Cancer (AJCC) has designated staging by TNM classification.[1]

Primary Tumor (T)

• TX: Primary tumor cannot be assessed
• T0: No evidence of primary tumor
• Tis: Carcinoma in situ
• T1: Tumor invades lamina propria or submucosa
• T2: Tumor invades muscularis propria
• T3: Tumor invades through the muscularis propria into the subserosa or into the nonperitonealized perimuscular tissue (mesentery or retroperitoneum) with extension 2 cm or less*
• T4: Tumor perforates the visceral peritoneum or directly invades other organs or structures (includes other loops of the small intestine, mesentery, or retroperitoneum more than 2 cm, and the abdominal wall by way of the serosa; for the duodenum only, includes invasion of the pancreas)

* [Note: The nonperitonealized perimuscular tissue is, for the jejunum and ileum, part of the mesentery and, for the duodenum in areas where serosa is lacking, part of the retroperitoneum.]

Regional lymph nodes (N)

• NX: Regional lymph nodes cannot be assessed
• N0: No regional lymph node metastasis
• N1: Regional lymph node metastasis

Distant metastasis (M)

• MX: Distant metastasis cannot be assessed
• M0: No distant metastasis
• M1: Distant metastasis

Stage 0

• Tis, N0, M0

Stage I

• T1, N0, M0
• T2, N0, M0

Stage II

• T3, N0, M0
• T4, N0, M0

Stage III

• Any T, N1, M0

Stage IV

• Any T, any N, M1

References

1. Small intestine. In: American Joint Committee on Cancer.: AJCC Cancer Staging Manual. 6th ed. New York, NY: Springer, 2002, pp 107-112.