Melanocytic nevi in pregnancy: histologic features and Ki-67 proliferation index

Methods: Dermal nevi excised from pregnant women (n = 16) were compared with nevi from location- and aged-matched control patients (n = 15). Histologic features and Ki-67 proliferation index were evaluated. Results: Nevi in pregnancy were more likely to have dermal mitotic figures (62.5% vs. 13.3%, p = 0.028) and higher mitotic rates (1.44 vs. 0.20 mitoses/mm2, p = 0.0027) than control nevi. A distinctive histologic entity, termed superficial micronodules of pregnancy (SMOPs), was observed more frequently in the nevi of pregnancy (81.3% vs. 26.7%, p = 0.040), and showed consistent immunoreactivity for HMB45. There was a trend toward higher Ki-67 proliferation index in the nevi of pregnancy (3.0% vs. 1.0%, p = 0.073). Prominent multinucleated melanocytes were seen only in controls. There was no significant difference in pigmentation or irritation changes between groups. Conclusions: Dermal nevi removed during pregnancy show characteristic histologic features including increased dermal mitoses, superficial micronodules of pregnancy (SMOPs), and trend toward increased Ki-67 proliferation index. Chan MP, Chan MM, Tahan SR. Melanocytic nevi in pregnancy: histologic features and Ki-67 proliferation index.