Table 2.
TNM clinical classification for SB-NETs (WHO 2019)
| T—Primary tumora | |||
| Tx Primary tumor cannot be assessed | |||
| T0 No evidence of primary tumor | |||
| T1 Tumor invades mucosa or submucosa and size ≤ 1 cm in the greatest dimension | |||
| T2 Tumor invades muscularis propria or size > 1 cm | |||
| T3 Tumor invades through the muscularis propria into subserosal tissue without penetration of overlying serosa (jejunal or ileal) | |||
| T4 Tumor perforates visceral peritoneum (serosa) or invades adjacent structures or other organs | |||
| N—Regional lymph node metastasis | |||
| Nx Regional lymph nodes cannot be assessed | |||
| N0 No regional lymph node metastasis | |||
| N1 < 12 regional lymph node metastasis without mesenteric mass(es) > 2 cm in size | |||
| N2 ≥ 12 regional lymph node metastasis and/or mesenteric mass(es) > 2 cm in maximum dimension | |||
| M—Distant metastasis | |||
| Mx Distant metastasis cannot be assessed | |||
| M0 No distant metastasis | |||
| M1 Distant metastasis | |||
| M1a Hepatic metastasis only | |||
| M1b Extrahepatic metastasis only | |||
| M1c Hepatic and extrahepatic metastasis |
| Stage I | T1 | N0 | M0 |
|---|---|---|---|
| Stage II | T2, T3 | N0 | M0 |
| Stage III |
T4 Any T |
Any T N1, N2 |
M0 M0 |
| Stage IV | Any T | Any N | M1 |
SB-NETs small bowel neuroendocrine tumors, WHO World Health Organization
aFor any T, add (m) for multiple tumors