Soft bulge in the armpit is mainly considered to be related to breasts, boils or carbuncle, lipoma and so on. 1. paratesticular breasts: most common in women, mostly related to congenital developmental abnormalities, can grow in the armpit or axillary line, the texture is soft, and can be manifested as a soft bulge in the armpit without redness, swelling, pain and itching. 2. Skin boil or carbuncle: skin carbuncle belongs to the inflammation in the depth of hair follicle and the surrounding area, and skin boil belongs to the inflammation in the depth of hair follicle, which can be manifested as a soft bulge in the armpit, and may be accompanied by local redness, swelling, and even pus outflow and other symptoms. 3. Lipoma: benign tumor, mainly related to excessive fat deposition in the body, the lesion in the armpit also manifests as soft bulge in the armpit, mostly without pain and other symptoms, with slight mobility. The causes of soft bulges in the armpits are many and not limited to the above diseases, so it is recommended to go to the hospital in time to find out the causes and then actively treat them, so as not to delay the condition.