Atypical melanomas can be dastardly difficult to detect. There is no typical pattern of atypia.
However, the Cancer Council Australia’s new guidelines, published in the MJA this month, at least provide some framework to help detect these tumours before they are advanced.
The guidelines acknowledge the early detection of superficial spreading melanomas has improved, with a reduction in both the median tumour thickness and the melanoma mortality.
However, the incidence of atypical melanomas only being diagnosed when they thicker lesions remains high in Australia, partly because they are so difficult to spot.
Atypical melanomas come in many guises. They often have peculiar or absent pigmentation, atypical vessels and symmetrical pigment patterns, and by definition do not follow the ABCD diagnostic criteria (asymmetry, border irregularity, colour variegation and a diameter of more than 6mm) of classic melanomas.
The main culprits include nodular melanoma, desmoplastic melanoma and acral lentiginous melanoma. Different subtypes can be mistaken for: scars; non-melanoma skin cancer; nail trauma or infection; and may mimic a plantar wart or macerated tinea infection.
Despite the differences, the guidelines state there is usually one shared characteristic gives away their identity. Melanomas change over time.
“Perhaps the most helpful clinical feature of biologically significant melanomas is that they are changing, regardless of their other clinical features,” the MJA article stated.
“Any lesion that is changing in morphology or growing over a period of more than one month should be excised or referred for prompt expert opinion.”
The guideline authors suggest adding EFG (elevated, firm and growing) criteria to the traditional ABCD criteria when assessing skin lesions. And importantly, they also stipulate urgent action if the lesion satisfies this criteria at the one-month mark.
MJA 2017; 9 October