Nevus of Ito is a unilateral, benign, dermal melanocytosis that presents as a darkly pigmented patch on the side of the neck and shoulder in the distribution of the posterior supraclavicular and lateral cutaneous brachial nerves.

It shares clinical and histopathologic features, aside from location, with other dermal melanocytoses including nevus of Ota (trigeminal distribution), congenital dermal melanocytosis (formerly known as a Mongolian spot in the lumbosacral distribution), and dermal melanocyte hamartoma. Dermal melanocytoses are caused by an increased number of dermal dendritic melanocytes and can be congenital or acquired. All dermal melanocytoses are more often seen in patients of Asian or African descent, and nevus of Ito, in particular, is more common among females.

Unlike the more common congenital dermal melanocytosis, nevus of Ito lesions do not spontaneously regress and may darken or grow in size with puberty. These changes are thought to be secondary to ultraviolet radiation and hormonal influences. Patients have noted sensory changes in the area of the nevus of Ito. Extremely rarely, melanoma arising in a nevus of Ito has been reported.