Final answer:
A sebaceous cyst that occurs on the scalp, neck, or back is a closed, non-cancerous sac beneath the skin, often resulting from a blocked sebaceous gland. It is different from acne, which is a condition resulting from clogged hair follicles and infected sebaceous glands, typically manifesting as comedones.
Step-by-step explanation:
A sebaceous cyst, which usually occurs on the scalp, neck, or back, is a type of skin lesion that can manifest similarly to acne, which is a common skin disorder involving infected sebaceous glands. Sebaceous cysts, however, are typically non-cancerous cysts that occur beneath the skin and may develop as a result of a blocked sebaceous gland, often filled with sebum. Unlike acne, which is usually related to bacterial infection and clogged pores, sebaceous cysts are closed sacs that can grow larger over time.
While both conditions involve sebaceous glands, acne is known for its appearance on the face and back, primarily in areas rich in sebaceous glands. It arises when hair follicles become clogged by shed skin cells and sebum, leading to the formation of comedones such as whiteheads and blackheads. In contrast, sebaceous cysts do not necessarily arise from clogged hair follicles and do not typically result in the same type of skin disturbance with comedones.