Diagnostic Accuracy of Dermoscopy for Spitzoid Tumours in Adults

Spitzoid tumours (ST) represent a diagnostic chal-lenge and the accuracy of dermoscopy in these cases remains unclear. This retrospective study evaluated dermoscopic images collected from 2011 to 2016. Two dermatologists, blinded to clinical/ histopathological data, identified lesions with spitzoid dermoscopic patterns, using histopathology as the gold standard. Of 4,337 dermoscopic images, 240 (5.5%) showed spitzoid dermoscopic patterns (221 patients; median age 40; 57.9 % female). Histopathology revealed 23 % (55/240) ST, 62 % (149/240) non--spitzoid melanocytic lesions and 15 % (36/240) non--melanocytic lesions. Overall, 25.4 % (61/240) were malignant, mainly melanoma/melanoma metastases (50/240). Across excised tumours, 1.5 % (67/4,337) were ST. Sensitivity and specificity were 82.1 % (95% CI 70.8%-90.4%) and 95.7 % (95% CI 95%-96.3%), with an AUC of 0.88 (95% CI 0.84-0.93). Positive predictive value (PPV) was 22.9 % (95% CI 17.8%-28.8%), and nega-tive predictive value (NPV) was 99.7 % (95% CI 99.5%-99.9%). Starburst pattern was more frequent in ST (p=0.007). Linear vessels (OR 5.12; 95% CI 2.08-13.1) and glomerular vessels (OR 3.03; 95% CI 1.37-6.69) correlated with malignancy. Dermoscopy demonstrated high diagnostic accuracy and NPVnegative predictive value. However, low PPVpositive predictive value highlights limited specificity in adults; since one1 in four4 lesions with a spitzoid dermoscopic pattern was malignant, any spitzoid lesion in adults warrants high clinical suspicion.