This reference uses AJCC 8, confirmed current for this site on 4 November 2026. UICC TNM 9th edition, effective in 2026, is a separate system. Record the organisation, edition, anatomical location and c/p/yc/yp staging prefix. AJCC · UICC.
Breslow thickness and ulceration determine T. Regional N includes the number of involved nodes, whether they were clinically evident, and microsatellite/satellite/in-transit metastases. These definitions do not apply to uveal or mucosal melanoma.
Primary tumour T category
| Category | Breslow thickness | Ulceration |
|---|---|---|
| Tis | Melanoma in situ | Not applicable |
| T1a | Less than 0.8 mm | Absent |
| T1b | Less than 0.8 mm with ulceration; or 0.8-1.0 mm inclusive | Ulceration may be present or absent at 0.8-1.0 mm |
| T2a / T2b | Over 1.0 to 2.0 mm inclusive | a absent, b present |
| T3a / T3b | Over 2.0 to 4.0 mm inclusive | a absent, b present |
| T4a / T4b | Over 4.0 mm | a absent, b present |
Local disease: clinical versus pathological groups
| Stage | Clinical cTNM (N0 M0) | Pathological pTNM (N0 M0) |
|---|---|---|
| 0 | Tis | Tis |
| IA | T1a | T1a or T1b |
| IB | T1b or T2a | T2a |
| IIA | T2b or T3a | T2b or T3a |
| IIB | T3b or T4a | T3b or T4a |
| IIC | T4b | T4b |
In AJCC 8, pT1b N0 M0 is pathological stage IA, whereas cT1b N0 M0 falls under clinical stage IB. Record c versus p and do not mix groupings.
Stage III regional disease
N1a/N2a reflect one or two/three clinically occult positive nodes; N1b/N2b reflect clinically detected nodes; N1c is satellite, microsatellite or in-transit disease without involved regional nodes. N2c/N3c include nodes together with such nonnodal regional disease. Exact pathological IIIA-IIID grouping requires T and N combination, not merely a positive sentinel node.
Clinical regional disease is stage III. Pathological groups IIIA, IIIB, IIIC and IIID are not interchangeable prognostic labels.
Detailed N1a-N3c regional disease classification
Clinically occult metastases are typically identified during sentinel lymph node biopsy; clinically detected disease is apparent on examination or imaging and is verified as appropriate. Satellites, microsatellites and in-transit lesions are non-nodal regional metastases.
| N | Clinical definition |
|---|---|
| N1a | One clinically occult node; no satellite/in-transit disease |
| N1b | One clinically detected node; no satellite/in-transit disease |
| N1c | No involved nodes; microsatellite/satellite/in-transit disease present |
| N2a | Two or three clinically occult nodes; no non-nodal regional spread |
| N2b | Two or three involved nodes, at least one clinically detected; no non-nodal spread |
| N2c | One involved node plus satellite/microsatellite/in-transit disease |
| N3a | At least four clinically occult nodes; no non-nodal regional spread |
| N3b | Four or more nodes including clinically detected disease, or matted nodes; no non-nodal spread |
| N3c | At least two involved nodes or matted nodes plus non-nodal regional spread |
AJCC 8 T1a/b-T2a with N1a or N2a and M0 can fall into IIIA, whereas T4b with N3a/b/c and M0 is IIID. The number of positive nodes alone does not establish pathological stage IIIA-IIID: the full T/N combination matters.
The source for the detailed categories is the NCI Melanoma PDQ.
Stage IV metastatic categories
| M category | Site of distant spread | Note |
|---|---|---|
| M1a | Distant skin, subcutaneous sites or distant nodes | No visceral metastases. |
| M1b | Lung | With or without M1a. |
| M1c | Other non-CNS visceral sites | With or without lung disease. |
| M1d | Central nervous system | With or without other sites. |
Record normal versus elevated LDH as an M-category suffix. Any M1 is stage IV.
Pathology and clinical staging checklist
Maximum Breslow thickness, ulceration, pathology factors and margins; Clark level does not replace AJCC T.
Clinical nodes, indicated imaging, SLNB, microsatellites, satellites and in-transit disease.
Metastatic sites, CNS status, LDH, staging date and yc/yp where applicable.
Sources: NCI Melanoma PDQ; ESMO CPG; AJCC current staging.
Other staging systems
Educational reference, not a substitute for specialist MDT review or official AJCC protocols. Record the edition used and do not infer a stage group from a single image.