Review provides clues to amelanotic and hypomelanotic melanoma diagnosis

Skin cancers

By Natasha Doyle

10 Mar 2022

Clinicians may identify pale melanomas easier and earlier based on a review by an Australian dermatology centre of clinical characteristics and risk factors for the lesions.

Previously the traits of amelanotic and hypomelanotic melanomas (AHM) appeared highly variable, non-specific and difficult to differentiate from other benign and malignant growths — leading to later diagnoses and poorer prognoses.

The findings from this retrospective study of 1,228 melanomas consecutively diagnosed at at Southern Suburbs Dermatology, Sydney, between 2012 and 2020 “may heighten clinician alertness to the possibility of, and proficiency in, making this important diagnosis” and support better patient outcomes, according to the letter in Melanoma Research.

Making up 7% of all assessed melanomas, AHMs typically appeared on the head and neck, in patients 65 years’ and over, as raised lesions and alongside actinic keratoses but not other cutaneous malignancies.

Meanwhile, pigmented melanomas were often found on the trunk (P = 0.001, difference in anatomic site), in younger individuals (P = 0.040) and as flat lesions (P = 0.008).

Sex and personal or family history of cutaneous malignancy made no significant difference to AHM or pigmented melanoma development. Nor did skin phototype, although an effect may have been masked by the largely light-skinned cohort, the authors wrote, noting that other studies had found an association between phototype and pale melanomas.

Despite 22% of AHM patients having symptoms, cases were more likely to present for a skin check, less likely to be considered as melanoma on dermatologists’ provisional diagnosis and primarily punch biopsied while pigmented melanomas presented as lesions of concern (P = 0.033), were mostly taken as excisional biopsies (P = 0.002) and were symptomatic in 16% of patients.

The authors, led by Dr Joshua Farrell, didn’t seem surprised by any of their results. Regarding age and anatomic sites, wrote that previous studies had suggested that AHM pathogenesis “may rely more heavily on chronic actinic damage”.

“The relative propensity of AHM for the head and neck and its association with actinic keratoses would support this,” they wrote.

“Lack of an association with keratinocyte cancer was not unexpected owing to its high overall prevalence in the Australian population,” they added.

Further, AHMs are typically nodular, which likely explains the cohort’s large number of raised cases.

Although the clinicopathological mechanisms of AHM aren’t clear, they “more often begin in, or more rapidly transition to vertical growth than pigmented melanoma but have been shown to retain their melanocytic lineage and melanin-producing enzymes”.

Finally, punch biopsies are generally preferred for “well-defined lesions of suspected benign and nonmelanocytic origin; especially on cosmetically-sensitive areas such as the head and neck”.

Though unsurprising, the authors hope that defining these characteristics will better equip clinicians to identify pale melanomas at earlier stages and improve patient outcomes.

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