Hard lumps and bumps on the stomach may be caused by boils, scarring and malignant tumors. 1. Boils: If obvious redness, swelling, heat and pain appear in a short period of time, it is considered to be boils caused by localized bacterial infection, i.e. hard lumps and bumps on the stomach. It may be caused by the spread and aggravation of the infection due to the untimely treatment of the small localized folliculitis itself. 2. Scarring: hard lumps and bumps on the stomach may be proliferative scars or keloids formed locally after the inflammation subsides. 3. Malignant tumor: the bulging skin fibrosarcoma, lymphoma, or metastatic cancer on the skin on the stomach can be manifested as the local appearance of hard lumps. Therefore, if malignant tumors appear in the skin or lymph on the stomach, hard lumps and bumps will appear. There may be other reasons for the hard lumps on the stomach, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment under the guidance of the doctor.