Case report of pigmented spitz nevus: a diagnostic challenge in the pediatric age

Abstract

Spitz nevus is a benign melanocytic lesion, more common in young individuals, with a prevalence of 50–75% of cases occurring in patients under 20 years of age. Its clinical and dermoscopic presentation is variable, often mimicking features of melanoma, which makes differential diagnosis challenging and requires clinicopathological correlation. We report the case of a female patient, aged 1 year and 11 months, who presented with a pigmented lesion on the right knee with progressive growth over three months. Dermatological examination revealed a hyperpigmented brown-to-black papule with irregular yet well-defined borders. Dermoscopy showed an inverted network pattern, multiple central brown globules, a blue-white veil, shiny white structures, structureless areas, and fine peripheral streaks, raising the hypotheses of melanoma and pigmented Spitz nevus, highlighting the diagnostic complexity of atypical pigmented lesions at an early age. Histological examination demonstrated a well-circumscribed and slightly asymmetric melanocytic lesion, without additional histological signs of malignancy. The immunohistochemical profile (HMB-45 and SOX10 positive, PRAME negative, and low Ki-67 index) was consistent with conventional Spitz nevus. This case emphasizes the importance of differential diagnosis with pediatric melanoma, a rare neoplasm (<3% of childhood cancers) that presents clinical features distinct from those observed in adults, which may lead to delayed diagnosis due to the absence of classic malignancy criteria. It also highlights the diagnostic challenges of atypical pigmented lesions in childhood and the importance of early recognition combined with integrated clinical, dermoscopic, and histopathological evaluation.