Final answer:
A hemangioma is another name for a birthmark caused by the dilation of small blood vessels in the skin.
Step-by-step explanation:
The other name for a stain in the skin caused by the dilation of small blood vessels and commonly known as a birthmark is a hemangioma. A hemangioma is typically a benign tumour consisting of an abnormal buildup of blood vessels in the skin or internal organs. Unlike the other options listed, a hemangioma directly involves the blood vessels. Lentigo refers to a small pigmented spot on the skin with a clearly defined edge, surrounded by normal-appearing skin and usually occurring in the elderly. Melasma is a condition in which brown patches appear on the face, and a nevus is a more general term for a mole or birthmark that is present at birth or appears shortly afterwards.