Lump under the right breast on the rib cage

The right lower breast rests over ribs, cartilage, muscle, and the skin crease. A bump that moves with the skin may be a cyst or irritated follicle. A deeper area may be breast tissue, a muscle edge, cartilage, or a rib contour. A breast lump is a common presentation of breast cancer, but being on the right side or over a rib does not identify the cause.

Mention whether the finding is close to the breast fold, changes when you move your arm or twist, or feels different from the matching area on the left. The right-sided position alone does not make it more or less serious.

Inspect the skin without repeatedly pressing the area. Note when you first noticed it, whether it is tender, and whether its shape or size seems to change with movement or your menstrual cycle. Make an appointment for a new lump that remains, enlarges, becomes fixed, or differs from the opposite side. A clinician can examine both breasts and the chest wall and choose further assessment if indicated.

Get prompt medical advice for redness, warmth, fever, worsening swelling, marked pain, bloody nipple discharge, skin dimpling, a newly inverted nipple, or a lump in the armpit. Seek emergency care for severe chest pain, breathlessness, fainting, or sudden severe illness.

Ask whether the finding is in the breast or chest wall, whether the left side provides a useful comparison, whether imaging is appropriate, and what changes should trigger an earlier review.