There are many reasons for the lump on the edge of the underwear at the root of the thigh, and the common ones are inguinal lymphadenitis, sebaceous cysts, lipomas, boils and other diseases. 1. Inguinal lymphadenitis: Inguinal lymph nodes are infected by external pathogenic bacteria or metastasis of tumors, which will cause enlargement of lymph nodes, manifested as lumps at the edge of the underwear at the root of the thigh. 2. Sebaceous cysts: local hair follicles and sebaceous glands are distributed exuberantly, and sebaceous gland ducts may form cystic structures when they are blocked, which may also cause thigh root lumps on the edge of underwear. 3. Lipoma: due to the accumulation of mature adipose tissue in the thigh root, clinically, it mainly manifests as subcutaneous swelling, usually without conscious symptoms. There may also be thigh root lumps at the edge of the underwear. 4. boils: hair follicles and the surrounding soft tissues of the skin suppurative infection, the early stage will cause subcutaneous hard lump swelling, pain, may also cause thigh root panty edge lumps symptoms. There may be other reasons for the lumps on the edge of the underwear at the root of the thighs, so you need to go to the hospital in time for examination and treatment to clarify the cause.