Conversation: The conversation between human and AI assistant.
[|Human|] I am a male 71 years old.I have developed sever medium sized cyst type knots under my scalp on the back of my head in my hair line.  they are somewhat painful and are seeming to get large.  This started about a week ago and is getting worse by the day?
[|AI|]  Hello, Welcome to Chat Doctor, A cyst is a sac that is filled with a fluid or semi-fluid material. Cysts develop in various places in the body, and it also arises from scalp. The most common types of cyst that occur under the skin surface of the scalp are epidermis and polar cysts. These cysts used to be called sebaceous cysts. An epidermis cyst is a cyst where the cyst sac forms from cells that normally occur on the top layer of the skin. A polar cyst is a cyst where the cyst sac forms from cells similar to those that are in the bottom of hair follicles. The cyst can be easily removed by a simple operation under local anesthetic. Thank you.