Table 1.

Current American Joint Committee on Cancer TNM classifications and stage groupings of esophageal cancer (American Joint Committee on Cancer, 2002), slightly modified for clarity

TNM classifications
Primary tumor (T)
TX	Primary tumor cannot be assessed
Tis	Carcinoma in situ (noninvasive cancer)
T1	Tumor invades mucosa (T1a) or submucosa (T1b)
T2	Tumor invades muscularis propria
T3	Tumor invades adventitia
T4	Tumor invades adjacent structures
Regional lymph nodes (N)
NX	Regional lymph nodes cannot be assessed
N0	No regional lymph node metastasis
N1	Regional lymph node metastasis (cancer-positive lymph nodes)
Distant metastasis (M)
MX	Distant metastasis cannot be assessed
M0	No distant metastasis
M1	Distant metastasis (M1a†, M1b‡)
NonTNM cancer characteristics
Histopathologic type	Squamous cell carcinoma, adenocarcinoma
Histologic grade (G)
GX	Grade cannot be assessed
G1	Well differentiated
G2	Moderately differentiated
G3	Poorly differentiated
G4	Undifferentiated
Stage groupings
0	Tis	N0	M0
I	T1	N0	M0
IIA	T2–3	N0	M0
IIB	T1–2	N1	M0
III	T3	N1	M0
	T4	Any N	M0
IV	Any T	Any N	M1
IVA	Any T	Any N	M1a
IVB	Any T	Any N	M1b

^†M1a = metastases to select nonregional lymph nodes.

^‡M1b = other distant metastases.