A comparative analysis of clinical and sonographic features: cutaneous melanoma and melanocytic nevi

Background: Cutaneous melanoma (CM) ranks among the most lethal skin malignancies, with its global incidence rising steadily. Cutaneous melanocytic nevi (CMN), by contrast, are common benign lesions that rarely undergo malignant transformation. Despite their divergent biological behaviors, CM and CMN frequently present with overlapping clinical and ultrasonographic features, rendering preoperative distinction challenging. In this study, we aim to investigate and compare the clinical and sonographic characteristics of CM and CMN.

Methods: This retrospective analysis included nine cases of CM, 11 cases of compound nevi, and 22 cases of intradermal nevi, all examined by ultrasound and confirmed by postoperative histopathology. Clinical and sonographic features were compared among the three groups, including gender, age, lesion location, depth, maximum diameter, margin, morphology, hyperechoic spots, posterior acoustic enhancement, lateral acoustic shadow, and color Doppler flow imaging (CDFI) grade. Differences were evaluated between CM and CMN groups, as well as among the three groups.

Results: (I) Significant differences (all P<0.05) were found between CM and CMN groups for eight features: patient age, lesion location, depth, maximum diameter, margin, morphology, posterior acoustic enhancement, and CDFI grade. (II) Receiver operating characteristic (ROC) curve analysis showed that patient age exhibited excellent performance in distinguishing CM from CMN (sensitivity 88.9%, specificity 97.0%, and an area under the curve (AUC) 0.928 [95% confidence interval (CI): 0.798–1.000]). Maximum diameter also demonstrated good discriminatory value [sensitivity 77.8%, specificity 81.8%, AUC 0.882 (95% CI: 0.763–1.000)]. When combined, age and maximum diameter achieved optimal performance [sensitivity 88.9%, specificity 100%, AUC 0.929 (95% CI: 0.796–1.000); all P<0.05]. (III) The same eight features also showed significant intergroup differences across the three diagnostic groups (all P<0.05). (IV) ROC analysis indicated that maximum diameter offered moderate diagnostic value in differentiating compound nevi from intradermal nevi [sensitivity 63.6%, specificity 68.2%, AUC 0.661 (95% CI: 0.467–0.855)].

Conclusions: CM predominantly occurs in elderly individuals on the extremities. Ultrasonographically, CM is characterized by involvement of the full-thickness dermis and subcutaneous layer, a maximum diameter of ≥1 cm, poorly defined margins, an irregular or slightly irregular morphology, posterior acoustic enhancement, and abundant blood flow signals. Conversely, CMN predominantly affects younger individuals, most frequently on the head, neck, and face. On ultrasound, compound nevi typically involve the superficial dermis, while intradermal nevi most commonly involve the full-thickness dermis. Both types of CMN exhibit a maximum diameter of <1 cm, relatively well-defined margins, relatively regular morphology, absence of posterior acoustic enhancement, and non-abundant blood flow signals. The combination of age and maximum diameter significantly enhances specificity in distinguishing CM from CMN. Maximum diameter alone offers some value in differentiating compound nevi from intradermal nevi.