A case of a pigmented neurofibroma resembling a giant congenital melanocytic nevus

In the spectrum of neurofibroma, pigmented neurofibroma is a rare variant observed in patients with or without neurofibromatosis. It is histologically characterized by the presence of scattered melanin-laden pigmented cells within the neurofibromatous lesion. Herein, we describe a case of a 30-year-old man who presented with a large pigmented patch showing focal hypertrichosis on the upper back. The lesion had been present at birth and there was no other cutaneous features to support a diagnosis of neurofibromatosis. Histologically, a proliferation of melanocytes was evident in the epidermis and upper dermis and within underlying neurofibromatous tissue. This abnormality resulted in diagnostic difficulty in the differentiation between pigmented neurofibroma and large congenital melanocytic nevus with complete neurotization because of the clinical and histological similarities, In support of the use of immunohistochemical markers, the diagnosis of pigmented neurofibroma could be made.