Can a breast cancer lump be in the armpit, or are they always on breasts?

Yes: As breast tissue normally extends up into the armpit, it is possible to develop a breast cancer there. Furthermore, some breast cancers may cause enlargement of the lymph nodes that are normally found in the armpit, which can manifest itself as a palpable lump in the armpit.

Armpit & breast: Breast cancer lumps can be in the armpit or lymph node. This is the 1st place a cancer will spread before going to other areas of the body. If cancer is detected early, it should only be in the breast. This is why breast self exam and mammograms are so important.

Can be: The tail of the breast extends all the way up to the armpit.

Yes: In some women, developmentally, some of the breast tissue is found in the armpit or axilla. This is called polymastia. Changes in the size are typically related to hormonal changes like pregnancy or breast feeding. Although quite rare, breast cancer can even devlop there.

Breast or armpit: Breast cancer can occur in the armpit for two reasons. One - the breast tissue can extend toward/into the armpit. Two - breast cancer can spread to the lymph nodes of the armpit.