A 45-year-old man presents with a 1.8 mm thick primary melanoma on the back (Clark level IV), no ulceration, mitotic rate 2/mm². SLNB is performed and shows a positive sentinel node (metastatic melanoma). Current staging (AJCC 8th) makes him:
- A Stage IIB
- B Stage IIIC
- C Stage IIIB ✓
- D Stage IVA
Explanation
AJCC 8th edition melanoma staging: positive regional lymph node (even micro-metastasis on SLNB) defines Stage III disease. The T-category for the primary melanoma: 1.8 mm thick = T2a (1.0–2.0 mm, no ulceration). Positive sentinel node (N1a - micro-metastasis) with T2a = Stage IIIB (T2a N1a M0). Stage IIIC would require T3b/T4a/N2 or higher. Stage IIB is for T3b/T4a without nodal involvement. The positive SLNB upstages from the primary-only staging and triggers adjuvant systemic therapy consideration (anti-PD1 or targeted BRAF/MEK therapy if BRAF V600E mutant).
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.