Low attenuation intratumoral matrix: CT and pathologic correlation.

Diffuse low attenuation lesions on CT scans are caused by various pathologic conditions, especially differences of the intratumoral matrix. Low attenuation on CT scans was more defined than fat density and less than muscle density, the so-called near water density. We present representative cases of low attenuation lesions in correlation with their pathologic features. Intratumoral matrix showing diffuse low attenuation on CT was classified into eight groups: fatty degeneration/fatty metamorphosis, intracellular high lipid content, large amounts of lipid-laden macrophages, mucin-producing tumor, myxoid degeneration/myxoid matriX, massive necrosis, true cystic growth of the neoplasm, and massive edema. Lesions with fatty degeneration or intracellular high lipid content could be shown as negative CT attenuation. Knowledge of the neoplasms or disease processes that tend to have such pathology will lead to correct interpretation of CT scans of various organs.