nevus

Pl. nevi [L.] a circumscribed stable malformation of the skin and occasionally of the oral mucosa, which is not due to external causes; the excess (or deficiency) of tissue may involve epidermal, connective tissue, adnexal, nervous, or vascular elements; called also mole.

• blue n. — a dark blue nodular lesion composed of closely grouped melanocytes and melanophages situated in the mid-dermis.
• connective tissue n. — any nevus occurring in the dermal connective tissue and characterized by nodules, papules or plaques, or by combinations of such lesions. Histologically, there is inconstant focal or diffuse thickening and abnormal staining of collagen.
• epidermal n. — congenital skin tumors that do not contain melanocytes, which vary widely in appearance, size and distribution, and which are commonly hyperkeratotic.
• hair follicle n. — occur on the proximal extremities and have thick, brushlike hairs protruding.
• intradermal n. — a nevocytic nevus in which the nevus cells occur in nests in the upper part of the dermis, with no evidence of the proliferative process by which they originated.
• melanocytic n. — any nevus, usually pigmented, composed of melanocytes. See also melanoma.
• pigmented n., n. pigmentosus — one containing melanin; the term is usually restricted to nevocytic nevi (moles), but may be applied to other pigmented nevi.
• sebaceous n. — an epidermal nevus containing an overgrowth of sebaceous glands, frequently growing larger during puberty or early adult life, and rarely giving rise to a variety of new growths, including basal cell carcinoma.
• n. vascularis, n. vasculosus, vascular n. — a reddish swelling or patch on the skin due to hypertrophy of the skin capillaries. Seen on the scrotum of old dogs, sometimes bleeding.