Ultrasonography can demonstrate the homogeneity, while CT [computed tomography] can demonstrate the density of a mass lesion. If a mass appears echo-free at ultrasonography, but is denser than water at CT, a solid tumor with grossly uniform cellular structure (usually a lymphoma or sarcoma), or a hematoma or hemorrhagic cyst is likely. If the mass has water density at CT, a cystic lesion is confirmed. One case for each category is presented.