What can cause a tumor under my left-upper rib?

Several lesions: If a lesion is palpable under the left rib cage the origin is most likely abdominal in origin ranging from an enlarged spleen to a palpable lesion of splenic flexure of colon. In addition several retroperitoneal masses such as the giant schwannoma and an extensive non functional pheo of left adrenal can be palpated. Left upper rib is covered by left clavicle.