Becker's naevus, also known as Becker's melanosis, Becker's pigmentary hamartoma, Nevoid melanosis, and Pigmented Hairy Epidermal Naevus is a skin disorder predominantly affecting males. 

 

The naevus generally first appears as an irregular hyperpigmentation on the torso or upper arm, though other areas of the body can be affected, and gradually enlarges irregularly, becoming thickened and often hairy (hypertrichosis).

 

The naevus is due to an overgrowth of the epidermis, melanocytes (pigment cells), and hair follicles.

 

Becker's naevus was first documented in two young men with acquired melanosis and hypertrichosis in 1948 by Dr Samuel William Becker, an American dermatologist (1894–1964). Since then, this condition of melanosis has been termed Becker's naevus.