Sebaceous cyst: The term refers to either an epidermoid cyst, which originates from the skin, or a pilar cyst, which comes from hair follicles. These cysts are closed sacs that can be found under the skin of the entire body, except for the palms of the hands and soles of the feet. A cyst usually is a slow-growing lump that can move easily under the skin. A foul odor may be noticed from the overlying skin.
Epidermoid cysts result from the proliferation of epidermal cells within a circumscribed space of the dermis. Analysis of their lipid pattern demonstrates similarities to the epidermis. In addition, epidermoid cysts express cytokeratins 1 and 10, which are constituents of the suprabasilar layers of the epidermis. The source of this epidermis is nearly always the infundibulum of the hair follicle, as evidenced by the observation that the lining of the 2 structures is identical Studies have suggested that human papillomavirus (HPV) and exposure to ultraviolet light (UV) may play a role in the formation of some epidermoid cysts.
The primary symptom of a sebaceous cyst is a small lump under the skin. The lump usually is not painful. In some cases, however, cysts can get inflamed and become tender to the touch. There may be redness and/or increased temperature of the skin on the area of the cyst. Drainage from the cyst will appear grayish-white and cheese-like and will have a foul smell.
Doctors can usually make a diagnosis by looking at the cyst.
They may also scrape off skin cells and examine them under a microscope or take a skin sample (biopsy) for detailed analysis in the laboratory.
Incision and drainage