Answer: Intrarenal ectopic adrenal cortical tissue

Histology: Immediately in the subcapsular region, there is a nodule composed of nests and cords of cells. Some of these cells have abundant eosinophilic cytoplasm while others have distinctly vesicular cytoplasm appearing to contain liquid. The lesion is fused with the adjacent kidney and focally extends in between renal tubules. The lesional cells appear uniform without atypia or nucleoli.

Discussion: The histology of this nodule is typical of ectopic adrenal cortex. Ectopic adrenal tissue is always solely cortical without medullary tissue. The most common site of ectopic adrenal cortical tissue is in the region of the celiac axis. Relatively common sites include around the broad ligament near the ovary (23%), around the spermatic cord (9.3%), and adjacent to the testicular adnexa (7.5%). Approximately 6% of ectopic adrenal cortical tissue is seen within the kidney most often in the subcapsular region as seen in this case. Much more rarely one can see ectopic adrenal cortical tissue in sites such as the placenta, lung, and intracranial and dural regions. Most of these ectopic adrenal cortical tissues are silent without evidence of hyperfunctioning although rarely they maybe symptomatic.