Scalp cyst

A trichilemmal cyst is a common cyst that forms from a hair follicle, most often on the scalp, and is smooth, mobile and filled with keratin, a protein component found in hair, nails, skin, and horns. Trichilemmal cysts are clinically and histologically distinct from trichilemmal horns, which are much rarer and not limited to the scalp. [Source: Wikipedia ]