To better understand skin cysts, it helps to understand the anatomy of the skin.
The skin contains three main layers:
- The superficial layer that makes up the surface of the skin
- It is composed of skin cells and can be divided into 5 layers based on cell type.
- The top layer of the epidermis, the stratum corneum, is made of dead, flat skin cells that shed about every 2 weeks.
- The thickness of the epidermis varies, according to location: it is very thick over the soles of the feet, and very thin over the ears.
- Lies beneath the epidermis
- Also varies in thickness depending on the location of the skin. It is .3 mm on the eyelid and 3.0 mm on the back.
- The dermis is composed of 2 layers that contain a connective tissue called collagen
- The dermis contains blood vessels, nerves, sweat glands, and hair follicles.
- The number of structures in the dermis varies, according to location.
- The dermis under the arms contains more sweat glands and hair follicles than the dermis on the back.
- Subcutaneous layer:
- Mainly fat and connective tissue.
- Contains blood vessels and nerves.
- Kwittken J. Sebaceous cyst: fact, not fiction. Int J Dermatol. 1994 Mar;33(3):218-9. 
- Nakamura M. Treating a sebaceous cyst: an incisional technique. Aesthetic Plast Surg. 2001 Jan-Feb;25(1):52-6. 
- Thaller SR, Bauer BS. Cysts and cyst-like lesions of the skin and subcutaneous tissue. Clin Plast Surg. 1987 Apr;14(2):327-40.