Staging
AJCC 8 melanoma, BWH for cSCC, AJCC 8 dedicated systems for MCC, conjunctival and Merkel. Imaging thresholds, SLNB indications, perineural-spread workup, and the pre-MDT data that determine treatment selection.
Melanoma — AJCC 8
AJCC 8 (Gershenwald 2017, in force from 2018) is the UK standard. Use the interactive melanoma staging calculator to map a Breslow / ulceration / mitotic / SLNB combination to the stage group.
T-category
| T | Breslow | a/b qualifier |
|---|---|---|
| T1 | < 0.8 mm (no ulceration); or < 1.0 mm with ulceration; or 0.8–1.0 mm any | T1a / T1b — note AJCC 8 redrew the boundary at 0.8 mm |
| T2 | 1.01–2.0 mm | T2a no ulceration · T2b ulcerated |
| T3 | 2.01–4.0 mm | T3a / T3b |
| T4 | > 4.0 mm | T4a / T4b |
Mitotic rate is reported in the RCPath dataset but is no longer a determinant of T1a vs T1b in AJCC 8 — that was an AJCC 7 rule.
N-category
The N1c trap: in-transit, satellite or microsatellite metastases ONLY (no involved regional nodes) = N1c. Add one node → N2c. ≥ 2 nodes or matted + in-transit / satellite / microsatellite → N3c.
M-category
M1a distant skin / soft tissue / non-regional nodes · M1b lung · M1c other non-CNS visceral · M1d CNS. Each is further qualified by LDH (0 = normal; 1 = elevated). AJCC 8 added M1d as a separate sub-category, reflecting the prognostic weight of brain disease.
cSCC — BWH first, AJCC 8 for H&N
BAD 2020 recommends the Brigham & Women's (BWH) T-stage in preference to AJCC 8 for cSCC — it outperforms AJCC 8 for prognostic discrimination in most cohorts. Use the on-site BWH staging calculator.
| BWH | Risk factors | Nodal metastasis | Death |
|---|---|---|---|
| T1 | 0 | < 1% | ≈ 0% |
| T2a | 1 | ~ 5% | ~ 1% |
| T2b | 2–3 | ~ 20% | ~ 10% |
| T3 | 4 (or bone invasion) | > 50% | > 30% |
BWH counts four high-risk factors: diameter ≥ 2 cm, poor differentiation, PNI of a nerve ≥ 0.1 mm calibre, and invasion beyond subcutaneous fat (excluding bone). Bone invasion is automatic T3. For head & neck cSCC, the AJCC 8 dedicated chapter is also used by many MDTs — its T-criteria incorporate size, depth > 6 mm, PNI of a named nerve, and bone erosion.
PNI sub-criteria
Any ONE of: nerve calibre ≥ 0.1 mm; PNI deeper than dermis; PNI of a named nerve. Single small-calibre dermal-twig PNI alone does not qualify as high-risk PNI.
BCC — staging is rarely formal
BCC almost never metastasises; formal staging is reserved for locally advanced or rare metastatic BCC requiring imaging. Subtype (low- vs high-risk histology — morphoeic / infiltrative / micronodular / basosquamous), depth and margins drive management decisions.
Merkel cell carcinoma
AJCC 8 MCC chapter. Localised disease (clinically node-negative) requires SLNB at the time of WLE for accurate staging — occult nodal involvement is common in MCC. PET-CT is standard at baseline per the EADO 2022 consensus to detect occult distant disease.
Conjunctival melanoma
Has its own AJCC 8 chapter — distinct from cutaneous and uveal melanoma. Managed by ocular oncology / oculoplastic surgery.
SLNB indications (melanoma — NICE NG14 §1.4.3–4)
- Do not offer SLNB for stage IA melanoma.
- Consider SLNB for Breslow 0.8–1.0 mm melanoma with ulceration, lymphovascular invasion or mitotic index of 2/mm² or more, after discussion of benefits, risks and uncertainty.
- Consider SLNB for Breslow > 1.0 mm melanoma after discussion of benefits, risks and uncertainty; this includes T2b and thicker tumours, but NG14 frames the decision as shared consideration rather than an automatic rule.
- SLN status changes stage (any involved SLN = at least N1a; stage III) and triggers adjuvant ICI / BRAF/MEK discussions per the relevant NICE TAs.
- Completion lymphadenectomy after SLN+ is no longer standard in most patients (MSLT-II: no OS benefit). Observation + adjuvant ICI is the modern UK default; lymphadenectomy is reserved for selected high-burden / extracapsular cases at MDT.
Imaging — what to ask for, when
| Indication | Modality | Notes |
|---|---|---|
| Stage 0–IIA melanoma, asymptomatic | No routine imaging | Per NICE NG14. |
| Stage IIB+ melanoma, baseline | CT TAP ± MRI brain | Per NG14 + local MDT protocol. |
| Stage III/IV melanoma | CT TAP + MRI brain | Brain MRI more sensitive than CT for melanoma metastases. |
| cSCC with named-nerve PNI | MRI head/neck with gadolinium + fat-saturation | The standard for perineural spread workup. Specifically request review of the relevant nerve tract. |
| High-risk cSCC (BWH T2b/T3) | USS regional nodes ± CT | USS is high-sensitivity for nodal disease. |
| Merkel cell carcinoma | PET-CT at baseline ± MRI brain | EADO consensus. |
| Suspected mucosal / uveal melanoma | Site-specific imaging | Coordinate with ocular oncology / H&N team. |
| Adnexal carcinoma with high-risk features | CT TAP per MDT | Hidradenocarcinoma, porocarcinoma, MAC etc. |
Pre-MDT package
By the time a case reaches MDT, you ideally have:
- Confirmed histology with RCPath-dataset reporting
- BWH / AJCC stage with the working calculator output
- Imaging where indicated, with formal report
- SLNB result if performed
- BRAF / MMR / MCPyV ancillary results as relevant
- Patient performance status, comorbidity profile, immunosuppression status, prior radiotherapy / treatment
- Patient preferences and family / social context — pertinent to surgical fitness and reconstruction decisions