A sebaceous cyst is a small non-cancerous lump or bump on the skin. It is usually found on the face, neck, upper chest and upper back but can also appear on other body parts. It develops gradually develops beneath the skin and is dome-shaped and smooth in appearance and there is no pain.
However, a sebaceous cyst can become infected and emit a foul odour, sometimes with an accompanying discharge of a cheese-like substance. An inflammed and infected cyst can cause tenderness and pain.