Painful lump under the breast at the bra line

A painful lump under the breast at the bra line may be caused by skin irritation, an inflamed cyst, muscle strain, or breast tissue changes. Pressure from a bra, sweating, and friction can affect the skin fold, while a deeper lump needs clinical assessment rather than guessing from its position.

A tender surface bump with redness may be an irritated hair follicle, boil, or blocked skin cyst. Pain after exercise or lifting can come from the chest-wall muscles or ribs. Breast tissue extends toward the side of the chest, so a lump near the bra line may still be breast-related. Breast cancer can present as a breast lump, but a painful lump does not by itself identify the cause; many benign problems can feel tender.

Look at the skin without repeatedly squeezing the area. Note whether the lump is superficial or deep, whether it moves, and whether its size changes with your menstrual cycle. Wear a supportive bra that does not rub, keep the fold dry, and use a warm compress for a tender skin bump. Arrange a clinician appointment for a new lump that persists, grows, returns, or cannot be clearly felt in the skin. Examination may lead to imaging.

Seek prompt care for rapid swelling, spreading redness, fever, pus, a firm fixed lump, skin dimpling, nipple inversion, bloody discharge, or a new change in the breast or armpit. Urgent help is needed if severe pain occurs with feeling very unwell.

Is the lump in the skin, chest wall, or breast tissue? Do I need an ultrasound or another examination? Which changes should prompt me to return sooner?