The American Joint Committee on Cancer (AJCC) has designated staging by the TNM classification as follows:[1]

TNM Definitions

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 muscle layer
  • T1a: Tumor invades lamina propria
  • T1b: Tumor invades the muscle layer
• T2: Tumor invades the perimuscular connective tissue; no extension beyond the serosa or into the liver
• T3: Tumor perforates the serosa (visceral peritoneum) and/or directly invades the liver and/or one other adjacent organ or structure, such as the stomach, duodenum, colon, or pancreas, omentum or extrahepatic bile ducts
• T4: Tumor invades main portal vein or hepatic artery or invades multiple extrahepatic organs or structures

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

AJCC Stage Groupings

Stage 0

• Tis, N0, M0

Stage IA

• T1, N0, M0

Stage IB

• T2, N0, M0

Stage IIA

• T3, N0, M0

Stage IIB

• T1, N1, M0
• T2, N1, M0
• T3, N1, M0

Stage III

• T4, any N, M0

Stage IV

• Any T, any N, M1

LOCALIZED (STAGE I)

These types of patients have cancer confined to the gallbladder wall that can be completely resected. They represent a minority of cases of gallbladder cancer. Patients with cancers confined to the mucosa have 5-year survival rates of nearly 100%.[2] Patients with muscular invasion or beyond have a survival of less than 15%. Regional lymphatics and lymph nodes should be removed along with the gallbladder in such patients.

UNRESECTABLE (STAGE II–IV)

With the exception of some patients with focal stage IIA disease, these types of patients have cancer that cannot be completely resected. They represent the majority of cases of gallbladder cancer. Often the cancer invades directly into adjacent liver or biliary lymph nodes or has disseminated throughout the peritoneal cavity. Spread to distant parts of the body is not uncommon. At this stage, standard therapy is directed at palliation. Because of its rarity, no specific clinical trials exist; however, such patients can be included in trials aimed at improving local control by combining radiation therapy with radiosensitizer drugs.

References:

1. Gallbladder. In: American Joint Committee on Cancer.: AJCC Cancer Staging Manual. 6th ed. New York, NY: Springer, 2002, pp 139-44.
2. Shirai Y, Yoshida K, Tsukada K, et al.: Inapparent carcinoma of the gallbladder. An appraisal of a radical second operation after simple cholecystectomy. Ann Surg 215 (4): 326-31, 1992.