Can Dermoscopy Be Used to Predict if a Melanoma Is In Situ or Invasive?

Abstract

Background: The preoperative prediction of whether melanomas are invasive or in situ can influence initial management.

Objectives: This study evaluated the accuracy rate, interobserver concordance, sensitivity and specificity in determining if a melanoma is invasive or in situ, as well as the ability to predict invasive melanoma thickness based on clinical and dermoscopic images.

Methods: In this retrospective, single-center investigation, 7 dermatologists independently reviewed clinical and dermoscopic images of melanomas to predict if they were invasive or in situ and, if invasive, their Breslow thickness. Fleiss' and Cohen's kappa (κ) were used for interobserver concordance and agreement with histopathological diagnosis.

Results: We included 184 melanomas (110 invasive and 74 in situ). Diagnostic accuracy ranged from 67.4% to 76.1%. Accuracy rates for in situ and invasive melanomas were 57.5% (95% confidence interval [CI], 53.1%-61.8%) and 81.7% (95% CI, 78.8%-84.4%), respectively. Interobserver concordance was moderate (κ = 0.47; 95% CI, 0.44-0.51). Sensitivity for predicting invasiveness ranged from 63.6% to 91.8% for 7 observers, while specificity was 32.4%-82.4%. For all correctly predicted invasive melanomas, agreement between predictions and correct thickness over or under 1.0 mm was moderate (κ = 0.52; 95% CI, 0.45-0.58). All invasive melanomas incorrectly predicted by any observer as in situ had a thickness <1.0 mm. All 32 melanomas >1.0 mm were correctly predicted to be invasive by all observers.

Conclusions: Accuracy rates for predicting thick melanomas were excellent, melanomas inaccurately predicted as in situ were all thin, and interobserver concordance for predicting in situ or invasive melanomas was moderate. Preoperative dermoscopy of suspected melanomas is recommended for choosing appropriate surgical margins.

Keywords: Breslow thickness; Dermoscopy; Inter Observer Variability; Melanoma; Projections and Predictions.

Figure 1

Dermoscopic images of the 4 invasive melanomas that were predicted as in situ by all observers. All 4 lesions had a Breslow thickness ≤0.5 mm. Lesions (a) and (b) were located on the upper extremities, and lesions (c) and (d) were located on the scalp and arm, respectively.

Figure 2

Sensitivity and specificity for the classification of invasive melanomas, for 7 dermatologists and for the majority decision (ie, decision of ≥4 observers).