A bulge in the right armpit without pain may be caused by paratesticular breast, sebaceous cyst, lipoma, enlarged lymph nodes and so on. 1. Associate breast: In addition to the normal breast, due to congenital developmental abnormalities caused by the phenomenon of new breast tissue in the axilla or axilla, which will lead to the phenomenon of a bulge in the right armpit, usually there is no obvious discomfort, and when some patients have menstrual periods, abnormal hyperplasia may occur, and even symptoms of pain. 2. Sebaceous cysts: if you don’t pay attention to the hygiene of the right armpit for a long time, the local sebaceous gland ducts will be blocked, and the sebum will gradually silt up to form the phenomenon of retention cysts, which can be existed for many years without any conscious symptom, and therefore it can be manifested as a bulge in the right armpit but not painful phenomena. 3. Lipoma: Lipoma in this case is usually painless. 4. Enlargement of lymph nodes: axillary lymph nodes have more distribution, chronic infection of lymph nodes, tuberculosis infection will lead to painless enlargement; while metastasis of malignant tumors or lymphoma invasion of lymph nodes here will lead to painless enlargement, and hard and enlarged lymph nodes can be touched. There are many reasons why there is a bulge in the right armpit but it does not hurt, so you should go to the hospital in time to have a relevant checkup and get a clear diagnosis and then be treated accordingly.