In this paper, we describe the case of an adult male with a pulmonary valve blood cyst. Blood cysts are benign primary heart tumors, common in neonates, but very rare in adults, mostly asymptomatic, and detected incidentally. Ultrasound (transthoracic transephophageal echocardiography) is crucial in detecting lesion, with the help of other diagnostic methods (MRI, CT). Further treatment, conservative or surgical, depends on the effect of the cyst on heart function. Although the diagnosis of cardiac lesions using routine imaging is available, definitive diagnosis is possible only by pathohistological and immunohistochemical analysis of the surgical sample.