A hard lump in the armpit, without pain as well as itching, needs to be further combined with a color ultrasound examination of the armpit. Because of the many causes, a common one is parametrium in the armpit. This disease is a congenital developmental abnormality, caused by incomplete degeneration of the breast tissue during the embryonic period, and is manifested as a locally elevated mass, which is similar to the feeling of touching the breast gland on palpation, with a soft texture and clear borders. The increase in the size of the parametrium is also affected by the hormonal level of the body, especially during pregnancy, after childbirth and during breastfeeding. There are also patients with enlarged lymph nodes in the armpit, which can be caused by local soft tissue injury after exertion or trauma. In addition, patients with breast enlargement may also show secondary enlargement of axillary lymph nodes.