Clinical and dermoscopic features of atypical melanoma

BACKGROUND: Melanoma is one of the most aggressive skin tumors, the incidence of which is increasing. Dermatoscopic diversity and imitation of other skin tumors lead to erroneous diagnoses and the choice of incorrect tactics. AIM: To identify clinical and dermatoscopic features depending on the thickness of atypical invasive melanoma that mimics other benign and malignant skin neoplasms. MATERIALS AND METHODS: The study was carried out at the Clinical and Diagnostic Department at the University Clinic of Privolzhsky Research Medical University for the period from January 2018 to December 2022. A total of 3957 medical records of patients who applied to the center with skin neoplasms were analyzed, among them 270 cases of skin melanoma were identified, 57 of which had a clinical and pathomorphological discrepancy between the preliminary and final diagnosis (atypical), were further divided into subgroups by Breslow thickness ― thin 0.8 mm (n=37) and thick ≥0.8 mm (n=20), for comparative analysis 70 melanomas were taken as a control group (typical). RESULTS: Atypical thin melanomas were more common in young patients aged 40 versus 57 years (p=0.000) and were characterized by a smaller average diameter ― 8 mm versus 10 mm (p=0.000). Clinically, cases of atypical thin melanoma differed in the following features: asymmetry 83.7% versus 100% (p=0.011), polychromy 70.1% versus 89.2% (p=0.043), smooth borders 27.1% versus 8.1% (p=0.032), cases of atypical thick melanoma differed in: asymmetry 71% versus 97.1% (p=0.004) and smooth borders 60% versus 14.7 (p=0.001). Dermoscopically, cases of atypical thin melanoma were characterized by the following features: polychromy 81.1% vs. 100% (p=0.005), atypical pigment network 67.6% vs. 94.6% (p=0.003), white streaks 16.3% vs. 40.5% (p=0.020), structureless area gray/gray-blue color 54.1% vs. 78.4% (p=0.027), punctate vessels 27.1% vs. 5.4% (p=0.012), glomerular vessels 13.5% vs. 0 (p=0.021); atypical thick melanoma cases differed in: atypical pigment network 25% vs. 79.4% (p=0.000), dots/globules at the periphery 15% vs. 41.2% (p=0.045), structureless area black/dark brown/brown 75% vs. 97.1% (p=0.013), structureless area gray/gray-blue 55% vs. 94.2% (p=0.001), structureless area red/pink 65% vs. 88.2% (p=0.041). CONCLUSION: Statistically significant clinical and dermatoscopic features that are not characteristic of typical melanoma characterize atypical melanomas.