The Second step
Once the diagnosis of a melanocytic lesion has been made we firstly look for one of the two negative features to decide if the lesion is benign or malignant
a. Symmetrical pigment Pattern
Lesion 1 is obviously symmetrical
Lesion 2 is symmetrical in one axis.
Lesion 3, an obvious melanoma, is asymmetrical in both axes.
b. Is there just a single colour?
Or more than 1 colour
The next step is to look for at least one of the 9 positive features.
These are:-
Blue-white veil
Multiple Brown Dots
Pseudopods
Radial streaming
Scar like depigmentation
Peripheral Black dots and globules
Multiple (5-6) colours
Multiple blue-gray dots
Broadened network
Blue-White Veil
Blue white veil is an indistinct, irregular, confluent blue pigmentation with an overlying white ground-glass haze. This represents histologically aggregated pigmented cells in the dermis (blue) overlaid by compact orthokeratosis. The pigmentation only occupies part of the lesion and is found mainly in papular areas.
Multiple Brown Dots
Dots are small round structures less than 0.1 mm in diameter and brown dots represent focal accumulations of melanin at the dermo-epidermal junction. In melanoma the dots are typically irregularly distributed.
Pseudopods
Are finger like projections of light brown to black pigment, which may terminate in small bulbous structures, at the periphery of the lesion and either connected to the lesion or the pigment network. Typically in melanoma, they are distributed patchily around the circumference of the lesion.
Lesion 1 is an in-situ melanoma; although pseudopods are reported to be uncommon in in-situ melanoma, my experience is that they occur fairly frequently as in the evolving melanoma in-situ shown below:-
Sometimes appearances can be misleading as in this lesion 2:-
SPECIMEN/CLINICAL NOTES: Lesion back. Enlarging lesion with pseudopods.
Sections show a compound melanocytic naevus which has undergone partial
regression of its dermal component with the presence of clumps of deeply
pigmented macrophages within the lesion. These latter features
presumably explain the clinically observed "pseudopods".
The lesions has a symmetrical architecture and exhibits no features of
malignancy or of dysplasia.
Radial streaming
In melanoma radial streaming or streaks as they are known in other algorithms, are distributed irregularly within the lesion. Symmetrical distribution is characteristic of Radial streaming is histopathologically identical to Pseudopods.
Both radial streaming and a broadened network can be seen in this 0.3mm superficial spreading melanoma on the anterior lower leg.
Scar like depigmentation
This feature indicates regression and appears as white coloured area lighter than the surrounding skin, this is often described as a “reverse network” and histopathologically features fibrosis, loss of pigmentation, epidermal thinning, and effacement of the rete ridges with melanin granules free in the epidermis or in melanophages.
Lesion 1 shows Scar like depigmentation in a 0.7mm superficial spreading melanoma on the back of a 75 year old male. Note the depigmentation is paler than the surrounding skin.
Lesion 2 shows a paler area which still has vessels present representing a hypomelanotic area in a SSM. This area is the same colour as or more commonly, pinker than the surrounding skin.
Peripheral black dots and globules
Represent accumulation of pigment in stratum corneum as a result of pagetoid spread of malignant melanocytes. Characteristically they are peripherally located and intensely black as opposed to brown globules often seen in benign lesions.
Lesion on the scalp of 70 year old noticed after he had a hair cut! 0.3mm SSM.
The blood spots are from the local anaesthetic injections of my over enthusiastic nurse!
Multiple Blue Gray Dots
These structures represent another feature of regression which is very common in Superficial spreading melanoma. Described as “pepper-like” they represent collections of melanin carrying macrophages (melanophages). Large collections of these structures are responsible for the blue white veil appearance. They are often a useful clue for the diagnosis of hypomelanotic melanoma, as in this case of an asymptomatic 0.6 ssm, noticed by the patient's wife.
Multiple (5-6) Colours
The colours in question are red, tan, dark brown, black, gray and blue. Multiple colours indicate increased vasculature in association with melanin distributed from the stratum corneum to the dermis.
Broadened network
Representing expansion of melanocytic nests at the dermo-epidermal junction and manifested by the thickening of the cords or lines in the network of a melanocytic lesion.
