Small lumps can be felt on the chest when lying down, which may be related to breast hyperplasia, breast fibroma, breast cancer, and so on. 1. Breast hyperplasia: it is a benign breast disease during breast development, mainly due to hormone imbalance, elevated prolactin, etc. It is often manifested as breast pain, nodules or lumps, and patients with breast hyperplasia may feel lumps in the chest when lying down, and it disappears after getting up. 2. Breast fibroma: Breast fibroma is a common benign disease of the breast, caused by the abnormal increase in the sensitivity of breast tissue to estrogen, painless lumps in the breasts, most of which can be touched when swimming or bathing, and can be accompanied by pain. 3. Breast cancer: proliferation of breast epithelial cells, malignant changes, the cause of which is still unclear, often painless breast lumps, axillary lymph node enlargement, nipple overflow, etc. Early breast cancer patients have no pain, and when lying down, they will feel the presence of lumps, which have a less than smooth surface and are not easy to push. When small lumps appear in the chest, you should consult a doctor in time to find out the cause of the disease and treat the symptoms under the regular guidance of the doctor.