Plexiform neurofibroma masquerading as a giant congenital melanocytic nevus

A 4-month-old male presented for a large, hypertrichotic brown patch on the upper back with several scattered 0.5-1.5 cm, round to oval, brown macules and patches on the trunk and extremities. The lesion was initially diagnosed as a giant congenital melanocytic nevus based on clinical exam and histopathology with immunohistochemical stains. The patient was later diagnosed with neurofibromatosis type 1, and the lesion on the back developed a "bag of worms" texture consistent with a plexiform neurofibroma and found to harbor a pathogenic variant in the NF1 gene. This case highlights the diagnostic challenge of differentiating these lesions and their overlapping clinical and histopathological features.