Severe architectural disorder is a potential pitfall in the diagnosis of small melanocytic lesions.

BACKGROUND: Little is known about the significance of severe architectural disorder in small melanocytic lesions with features of dysplastic nevi (DN).

METHODS: Using previously reported criteria, 355 consecutive DN were scored for architectural disorder and cytologic atypia. The DN were classified according to their size as small (equal or less than 3 mm) or large (greater than 3 mm).

RESULTS: Of these 136 (38.3%) DN were classified as small. Grades of architectural disorder and cytologic atypia were equally distributed in small and large DN. Forty lesions were diagnosed as dysplastic nevi with severe architectural disorder (DNSAD). Thirteen DNSAD were small; of these, 84.6% were junctional. DN showing only mild to moderate architectural disorder were found to be predominantly compound. DN with severe cytologic atypia were mainly large (8/10 cases) with no particular type (junctional or compound) predominance. Seven cases displayed both severe architectural disorder and severe cytologic atypia; only one of these cases (a junctional lesion) measured less than 3 mm.

CONCLUSIONS: Small melanocytic lesions displaying severe architectural disorder are mainly junctional and tend to show only mild cytologic atypia. Caution is needed when interpreting the degree of architectural disorder in these small melanocytic lesions, in order to avoid overdiagnosis of melanoma.