Authors report a case of a malignant psoas tumor diagnosed in a 69-year-old patient with an abdominopelvic CT scan as well as a PET-Scanner performed as part of the assessment of infective endocarditis extensions on aortic stenosis. Authors insist on the rarity of psoas tumors which remain mostly malignant, and on the interest of the CT scan and percutaneous biopsy for a precise histological diagnosis conditioning the therapeutic management. Treatment must be integrated into multidisciplinary approach where surgery occupies preponderant place. This case illustrates a therapeutic quandary regarding to timing of cardiovascular surgery related to carcinological surgery and the complement by radio and chemotherapy.