A pilar cyst, also known as a trichilemmal or isthmus-catagen cyst, is a benign (non-life-threatening) growth that, upon examination, looks identical to the more common epidermoid cyst, except that 90% of pilar cysts occur on the scalp. They tend to be more mobile and firmer than epidermoid cysts, and are derived from a different part of the hair follicle. The internal contents tend to be more "homogenous" and smooth. It is not uncommon to have multiple pilar cysts on the scalp and for the condition to run in families. Treatment is generally only for cosmetic reasons and excision with removal of the cyst and its contents is curative. The nice thing about these cysts is that they are often thicker-walled, so they can often be "popped" out whole, which not only ensures that I've removed it completely, but also leads to an extremely satisfying “pop!”