There is a round lump in the middle of the rib cage of newborns, which can be caused by lipoma, sebaceous cyst and other diseases. 1. Lipoma: lipomas are mainly caused by abnormal fat metabolism in the body, often occurring in the trunk, limbs and other parts of the body, usually not accompanied by pain, and can appear in the middle of the rib cage with a round pimple-like protrusion. 2. Sebaceous cysts: when the sebaceous glands of the local skin follicles in the middle of the ribs are blocked, the sebum gathering can form cysts, which in turn appear as round pimple-like sebaceous cysts. Newborns with a round lump in the middle of the ribs should seek medical attention in a timely manner, under the guidance of specialists to actively carry out appropriate treatment, which will help to alleviate the uncomfortable symptoms as soon as possible.