Adrenal gland: 15 week fetus
At this stage of development, the adrenal gland consists mostly of fetal cortex. There is a thin rim of definitive
(adult) cortex at the periphery (here in the upper margin). The groups of dark cells within the fetal cortex
are migrating neuroblasts which will form the adrenal medulla centrally. Sometimes these do not complete
their migration and form neuroblastoma-in-situ. These lesions are thought to usually resolve spontaneously.