Rationale and objectives: The authors' purpose was to determine whether computed tomographic (CT) attenuation values of fluid in breast cysts could be in the range of values for soft tissue and could be correlated with protein content of the fluid.
Materials and methods: Aspirate samples from 10 simple breast cysts were analyzed for protein content, and CT attenuation values were calculated by means of a breast phantom. A corrected attenuation value for breast-cyst fluid was calculated by using sterile water as a control.
Results: The mean corrected attenuation value for the cyst aspirate was 28.1 HU; most simple cysts have an attenuation value of only 10 HU. Protein concentration ranged from 0.9 to 2.4 g/dL. A significant, almost linear relationship was noted between protein content and attenuation value of cyst fluid (r = .85, P < .01).
Conclusion: The CT attenuation values of breast cysts can be in the range of those of soft tissue. This high attenuation value is correlated with the high protein content of breast-cyst fluid. Therefore, an apparent circumscribed soft-tissue mass seen within the breast at CT may represent a simple cyst.