Dermoscopy May Be More Accurate vs Incisional Biopsy for Melanoma Thickness

The use of dermoscopy in the disease course of malignant melanoma proved to be more accurate for diagnosing melanoma thickness compared with incisional biopsy, with the latter method carrying higher risks of understaging and inaccurate margin definition, according to the findings of an observational cross-sectional study published recently in Anais Brasileiros de Dermatologia.

“Melanoma thickness is a relevant prognostic marker that is crucial for staging, and its calculation relies on the histopathological examination,” the study authors wrote. “There is a risk of thickness underestimation with an incisional biopsy if the latter is not performed on a tumor area where the thickness is maximal.”

There were 119 patients included in this analysis, and their dermoscopic, demographic, and clinical variables were evaluated for their potential ability to predict melanoma thickness (≤1 mm, n = 59; >1 mm, n = 60). Most participants were 40 years or older (94.1%) and female (51.3%). All received care for cutaneous melanoma at the Dermatology and Venereology Service of Centro Hospitalar e Universitário de Coimbra, in Portugal, between January 2014 and December 2017.

Overall, the most common sites of malignant melanoma were the trunk (35.3%) and head and neck (27.7%); an upper limb (except for the hand) and the hand were the least common sites, at 5.9% and 3.4%, respectively. Melanoma thickness was close to balanced among the patients, with 49.6% having a thickness of 1 mm or thinner and 50.4% reporting more than 1 mm.

The top dermoscopic patterns with potential associations with melanoma thickness were a multicomponent pattern in 54.2% of those with a malignant melanoma thicker than 1 mm and a reticular pattern in 52.5% of those with a malignant melanoma of 1 mm or thinner. In both groups, a parallel ridge pattern (5.1% and 3.4%, respectively) held the smallest association with thickness.

Other variables considered were atypical pigment network/pseudo-network, negative pigment network, irregular dots and/or globules, depigmentation/hypopigmentation, striae/pseudopods, blue-gray veil, atypical vascular pattern, and white shiny lines. From among these, atypical pigment network/pseudo-network (P < .001) and negative pigment network (P = .027) had the strongest correlations with melanoma thickness of 1 mm or thinner, whereas atypical vascular pattern (P < .001) and white shiny lines (P = .003) correlated the most with melanoma thickness of greater than 1 mm.

When demographic and epidemiological variables were considered, age older than 40 years (P = .049) had a significant association with melanoma thickness of greater than 1 mm and was linked to a lower frequency of ephelides and previous sunburns (P = .032 for both). For thickness of 1 mm or thinner, only amelanotic melanoma, or the absence of pigmentation, had a significant association (P < .001).

However, following their multivariate logistic regression analysis, the authors determined that 1 variable each was associated with melanoma thickness or thinness: atypical vascular pattern for melanoma thicker than 1 mm (P < .001) and atypical pigment network/pseudo-network for 1 mm or thinner (P = .001).

“Dermoscopy is a potentially useful technique for reducing understaging errors, allowing the choice of the most appropriate site for the incisional biopsy,” the authors concluded, “which should avoid areas where there is only an atypical pigment network (related to inferior tumor thickness) and preferably focus on areas where atypical vessels are observed (associated with greater thickness).”

They recommend that future prospective studies be conducted to confirm their findings.

Reference

Silva ARC, Vieira RJDC. Predictive factors of melanoma thickness. An Bras Dermatol. 2022;97(5):601-605. doi:10.1016/j.abd.2021.12.002