Discovering a lump on your neck, back, or behind your ear can be unsettling—especially when it appears suddenly or feels unfamiliar. Many lumps turn out to be harmless, but some can point to an underlying health issue that deserves attention.Lumps can differ greatly in size, texture, and cause. Some fade away on their own, while others linger, return, or gradually enlarge. Knowing what might be causing a lump can help you understand how to care for it and recognize when it is time to get medical advice.This article outlines the most common reasons lumps form—especially epidermoid cysts—along with typical symptoms, ways people care for them at home, possible risks, and medical treatment options.

What Is an Epidermoid Cyst?An epidermoid cyst is a common, benign (non-cancerous) growth that develops just under the skin. These cysts usually grow slowly and can form almost anywhere, though they are most often seen on the neck, back, face, or behind the ears.They form when skin cells that normally shed become trapped beneath the surface. Those cells continue to multiply, creating a sac filled with keratin, a thick protein also found in hair and nails.Most epidermoid cysts do not cause pain and are generally harmless. However, they can become irritated or infected, which may lead to redness, swelling, tenderness, and discomfort.Although anyone can develop an epidermoid cyst, they tend to occur more often in adults—particularly men—than in children.