Table 2.
American Joint Council on Cancer TNM Rectal Cancer Staging System
| TMN Stage | Histopathology | Ultrasonographic Features |
|---|---|---|
| T, tumor; N, node; M, metastasis. | ||
| Tx | Primary lesion cannot be assessed | Tumor depth cannot be determined |
| T0 | No primary tumor identified | No tumor visualized |
| Tis | Carcinoma in situ (tumor limited to mucosa) | 1st hypoechoic layer is expanded, but 2nd hyperechoic layer is intact |
| T1 | Tumor invades submucosa, but does not involve muscularis propria | Middle hyperechoic layer is stippled or broken in appearance, but generally intact |
| T2 | Tumor invades muscularis propria | Middle hyperechoic layer completely disrupted; tumor may extend into 2nd hypoechoic layer |
| T3 | Tumor invades into perirectal fat/serosa | Outer hyperechoic layer disrupted |
| T4 | Tumor invades into neighboring organs/peritoneal cavity | Tumor extension into neighboring organs |
| Nx | Nodal metastasis cannot be assessed | |
| N0 | No nodal metastasis | |
| N1 | Involvement of 1–3 perirectal/pericolic nodes | |
| N2 | Involvement of ≥ 4 perirectal/pericolic nodes | |
| Mx | Distal metastasis cannot be identified | |
| M0 | No distal metastasis | |
| M1 | Distal metastasis present | |