Nodules are often caused under the skin of the back due to benign swellings such as lipomas, fibromas, or cysts. 1. Lipomas: These are single or multiple lung nodules, which are benign and usually harmless due to localized hyperplasia of mature adipose tissue. 2. Fibroma: after the inflammation subsides, localized scarring hyperplasia occurs, forming keloid nodules and keloid bumps, which are also more common back nodules. 3. Cysts: Sebaceous cysts, also medically called epidermal cysts, are commonly known as comedones. Due to the blockage of local sebaceous gland openings, the contents accumulate and gradually form intradermal and subcutaneous nodules. Back subcutaneous nodules are also seen in other causes, should be timely medical care, can be first local ultrasound clear diagnosis after targeted treatment, so as not to delay the condition.