Congenital nevocytic nevi: follow-up of a Swedish birth register sample regarding etiologic factors, discomfort, and removal rate.

Congenital nevi both small and large are frequently removed. We attempted to study the removal rate and etiologic aspects of congenital nevi as well as their psychosocial effects through the use of a quality test. A questionnaire sent to a sample population of individuals with congenital nevocytic nevi (n=192) collected from the Swedish Medical Birth Register (SMBR) was used as a test of the register's quality and for collecting information on rate of removal and etiologic factors. The quality test indicated that only 85.3% of the nevi listed in the SMBR were true congenital nevocytic nevi. Of all true congenital nevocytic nevi reported in the questionnaire, 39.8% had been removed and none of the rest had developed malignant melanoma. The median time for follow-up was 14 years. The median age at removal of the nevi was 9.7 years. Eight percent of respondents believed that the skin lesion caused taunting and changed their social activities. No infection or illness during pregnancy was specifically related to the development of congenital nevi. In conclusion, the larger the nevi, the more frequently and earlier they are excised. With an excision rate of 40% of congenital nevocytic nevi, we found no malignant melanoma.