Touching a prominent lump on the back is usually some benign skin and subcutaneous swelling, which is mostly considered to be caused by lipoma, sebaceous cyst, dermatofibroma and other diseases. 1. Lipoma: due to obesity, fat metabolism is not coordinated, local tissue hyperplasia, the formation of lipoma, manifested as a painless swelling on the surface of the body, preferably occurring in the trunk and limbs, with clear boundaries, pliable texture, no pressure pain, smooth surface and good mobility. 2. Sebaceous cyst, which is also a surface swelling, usually due to sebaceous gland duct obstruction, sebaceous gland cystic epithelium is gradually increased by the contents of the excessive expansion and the formation of cysts, if there is no infection, there will be no pain. 3. Dermatofibroma: mainly manifested in the part of the skin below the stratum corneum and above the granular layer, the skin is abnormally proliferated, which is the manifestation of skin cell variability. If you feel a prominent lump on your back without pain, it is recommended that you go to the hospital in time to find out the cause of the disease and target treatment to avoid delaying the condition and causing other damage.