Figure 17a. Lipoma with agenesis of the corpus callosum. (a) Coronal US image of a fetal head shows a midline, echogenic mass in the region of the corpus callosum (arrow). This appearance is characteristic of a lipoma, and the rest of the brain should be carefully evaluated for agenesis of the corpus callosum. (b) Photograph of the brain (infant died of other causes) demonstrates a lipoma (arrow), which corresponds to the mass seen at US. Note absence of the corpus callosum, which would normally be seen as a band of tissue connecting the two cerebral hemispheres.