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 organisation, edition, anatomical location and the c/p/yc/yp prefix. AJCC · UICC.
Cutaneous SCC, basal cell carcinoma and Merkel cell carcinoma require different frameworks. AJCC 8 head-and-neck cSCC staging is site-specific; recurrence risk is not interchangeable with a TNM stage.
Head and neck cSCC - AJCC 8
| T category | Criteria | Clinical note |
|---|---|---|
| Tis | Carcinoma in situ | No stromal invasion. |
| T1 | Greatest dimension ≤2 cm | When no higher T criterion is met. |
| T2 | >2 to ≤4 cm | No T3/T4 features. |
| T3 | >4 cm or minor bone erosion, perineural invasion or deep invasion | Deep invasion >6 mm or beyond subcutaneous fat; PNI depends on nerve calibre/site. |
| T4a | Gross cortical bone or marrow invasion | Requires local extent assessment. |
| T4b | Skull-base invasion and/or involvement of skull-base foramina | Full multidisciplinary evaluation. |
With N0 M0, Tis is stage 0, T1 stage I, T2 stage II and T3 stage III. Nodal status with extranodal extension (ENE) and T4 require complete site-specific grouping. Do not apply head-and-neck cSCC staging indiscriminately to trunk, extremity or eyelid tumours.
Head-and-neck cSCC clinical N and stage groups
ENE means extranodal extension. Pathological pN subcategories may differ from clinical cN. Both assessments should be documented separately.
| N | AJCC 8 |
|---|---|
| N0 | No regional nodal metastasis |
| N1 | One ipsilateral node ≤3 cm without ENE |
| N2a | One ipsilateral node >3 to ≤6 cm without ENE |
| N2b | Multiple ipsilateral nodes ≤6 cm without ENE |
| N2c | Contralateral or bilateral nodes ≤6 cm without ENE |
| N3a | Node >6 cm without ENE |
| N3b | Clinically evident extranodal extension |
AJCC 8: stage 0 - Tis N0 M0; I - T1 N0 M0; II - T2 N0 M0; III - T3 N0 M0 or T1-T3 N1 M0. Stage IV includes T1-T3 N2 M0, any T N3 M0, T4 any N M0, or any M1. Do not transfer this site-specific system to eyelid carcinoma or other skin locations.
Reference: NCI Skin Cancer PDQ.
BWH classification is risk stratification, not AJCC
| BWH T | Risk features | Interpretation |
|---|---|---|
| T1 | No factors | No listed high-risk features. |
| T2a | One factor | Evaluate recurrence and nodal risk. |
| T2b | Two or three factors | Higher-risk profile. |
| T3 | Four factors or bone invasion | Very high-risk phenotype. |
The four BWH factors are diameter ≥2 cm, poor differentiation, PNI of nerve ≥0.1 mm, and invasion beyond subcutaneous fat. Immunosuppression, recurrence, margins and site remain relevant independent considerations.
Basal cell carcinoma - risk usually matters more than stage
For most BCCs, document anatomical site, subtype, recurrent status, margin definition, invasion and perineural findings. Do not routinely label every BCC with a general AJCC I-IV stage; very advanced lesions may warrant site-specific TNM assessment.
Merkel cell carcinoma - distinct AJCC 8
| cTNM | Criterion | Clinical group at M0 |
|---|---|---|
| T1 | ≤2 cm | I if N0 |
| T2 | >2 to ≤5 cm | IIA if N0 |
| T3 | >5 cm | IIA if N0 |
| T4 | Invasion of fascia, muscle, cartilage or bone | IIB if N0 |
| N1-N3 | Regional nodal and/or in-transit involvement | Clinical stage III |
| M1 | Distant metastasis | Stage IV |
For MCC pTNM, IIIA includes clinically occult nodes found on SLNB and specified unknown-primary scenarios, while IIIB reflects clinically apparent nodal or in-transit disease. Keep cTNM and pTNM separate.
MDT pitfalls
High-risk BCC or cSCC does not automatically mean TNM stage III/IV.
Eyelid and other specialised skin sites can have distinct TNM rules.
SLNB in MCC, ENE in cSCC, immune status and pathological features are essential.
Sources: NCI Merkel PDQ; NHS cutaneous H&N TNM8; cSCC AJCC/BWH overview; AJCC editions.
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.