Cyst under the breast bra line: what to know

The bra line is where breast tissue, skin, sweat glands and friction meet. A lump may sit in the skin, under the skin, within breast tissue, or in the chest wall. It can feel smooth, tender, firm or mobile, and rubbing from a bra may make nearby skin sore. Appearance and touch alone cannot reliably identify the type of lump.

A clinician may ask when it appeared, whether it changes with the menstrual cycle, and whether there is redness, warmth, drainage or nipple change. An examination may be followed by imaging such as a breast ultrasound, which uses sound waves to look at a palpable area.

Arrange a clinical assessment for a new, persistent or changing lump. Until then, avoid squeezing, puncturing or repeatedly checking it, because this can irritate tissue and complicate healing. Wear a well-fitting bra or a softer layer if friction worsens discomfort, and note changes in size, tenderness, skin colour or drainage.

If assessment shows a simple cyst, the plan may be observation, review if it changes, or drainage when symptoms warrant it. Treatment depends on where the lump is and what the examination or imaging shows.

Seek prompt medical care if the area becomes rapidly more painful, red, hot or swollen, or if you develop fever, feel unwell, or notice pus-like drainage. Arrange assessment without delay for a hard fixed lump, skin dimpling, a new nipple inversion, bloody nipple discharge, or a lump that persists or grows.

Ask: Does the lump seem to arise from skin or breast tissue? Do I need a breast ultrasound? What changes should lead me to return sooner? If it is a cyst, would observation or drainage be more suitable?