Benign Proliferative Nodules in a Giant Congenital Melanocytic Nevus: Diagnostic Challenge and Management

Congenital melanocytic nevi are cutaneous malformations present at birth, resulting from a benign proliferation of melanocytes. Although generally benign, they can have significant psychological impacts and carry a non-negligible risk of progression to malignant melanoma. We report a case of a giant congenital melanocytic nevus associated with a perianal mass in an infant, two and half-month-old infant, with no notable medical history, born at term. He was referred for a pigmented perianal swelling located on a large hyperpigmented plaque covering the lower back, buttocks, perineum, external genitalia, and the upper third of the thighs, consistent with a giant nevus. Multiple pigmented maculopapular satellite lesions were present, extending from the scalp to the soles of the feet. All lesions had been present since birth. The general examination was unremarkable. Doppler ultrasound revealed a well-defined, homogeneous, hypoechoic subcutaneous lesion with low vascularity, and skin biopsy confirmed a benign proliferative nodule. The proposed management included surgical excision, neurological and growth development follow-up, and psychosocial support for the infant and the parents. Six months after surgery, follow-up showed no evidence of recurrence, with the infant demonstrating normal neurological function and appropriate growth and developmental progress. This case highlights the importance of an accurate clinical and histological diagnosis and a multidisciplinary approach to management. It contributes to the limited local data from Madagascar and may contribute to the understanding of potential complications and their management.