Why does hormone receptor-positive breast cancer cause a breast lump?

Hormone receptor-positive means the cancer cells have proteins that can respond to oestrogen, progesterone, or both. Those signals may encourage the cells to grow. As the cells multiply, they can collect in a localised mass that feels different from the surrounding breast. The lump may be hard, irregular, or less mobile, although feel alone cannot identify its cause.

Breast tissue can also contain cysts, fibroadenomas, hormonal changes, inflammation, or other benign lumps. A new lump therefore needs assessment rather than self-diagnosis. Examination and breast imaging help clinicians understand its shape and tissue features; a biopsy may be needed to identify the cells and check hormone receptors.

Arrange a clinical assessment for a new, persistent, or changing lump. Note when you first noticed it, whether it changes during your cycle, and any skin or nipple changes. Do not repeatedly press the area, because this can make it sore and harder to judge. Take any previous breast imaging or biopsy information to the appointment.

Seek prompt medical advice for a new lump, a lump that is enlarging, skin dimpling, nipple inversion, bloody discharge, or swelling in the armpit. Urgent care is appropriate if breast redness, marked warmth, severe pain, or fever develops, because infection can also need quick treatment.

Ask whether the lump needs ultrasound, mammography, or biopsy; whether testing shows hormone receptors; and how the findings affect treatment choices. You can also ask what changes should prompt an earlier review and when results will be available.