In situ or invasive? Read the colour

In_situ_vs_Invasive_Melanoma_Premium.mp4

Seven dermatologists judged 184 melanomas. They called the in situ ones correctly only 58% of the time. Once you have decided it is a melanoma, the next question decides the margin, the operation and sometimes the sentinel node: has it reached the dermis?

Three key points

Colour is a depth gauge. Melanin in the epidermis looks brown or black; melanin in the dermis looks grey or blue. Structures that need a dermal component signal invasion.
Red flags for invasion: blue-white veil (odds of invasion raised about 5- to 15-fold across studies), shiny white lines (about 5-fold), milky-red areas and lesions with little pigment.
Regression is in both. In situ melanomas tend to show a coarse, reticular grey-blue net with light brown areas. Invasive ones show structureless blue, white scar-like areas and a veil. Peppering alone does not help.

Pearl: Blue-white veil, shiny white lines and milky-red areas mean the melanoma has reached the dermis. Their absence does not prove in situ.

Your turn

Decide: Look at melanoma A and B in the video before the answer. Which one did you call invasive, and which clue made you decide?
Share your case: Post the thin invasive melanoma that looked in situ, or the in situ melanoma that looked invasive. Dermoscopy plus histology, please.
Myth or fact? "Regression structures mean the melanoma is still in situ." Reply with your answer and why.

Go deeper

References

Polesie S et al. Dermatol Pract Concept 2021;11:e2021079. doi:10.5826/dpc.1103a79

Lallas A et al. JAMA Dermatol 2018;154:414–419. doi:10.1001/jamadermatol.2017.6447

Seidenari S et al. Br J Dermatol 2010;163:302–309. doi:10.1111/j.1365-2133.2010.09821.x

Polesie S et al. Acta Derm Venereol 2021;101:adv00570. doi:10.2340/actadv.v101.281

Spadafora M et al. Exp Dermatol 2026;35:e70333. doi:10.1111/exd.70333

Silva VP et al. An Bras Dermatol 2013;88:712–717. doi:10.1590/abd1806-4841.20132017