Intrarenal ectopic adrenal tissue and renal-adrenal fusion: a report of nine cases.

Intrarenal ectopic adrenal tissue and renal-adrenal fusion are rare findings in the adult population. We reviewed seven cases of intrarenal adrenal tissue and two cases of renal-adrenal fusion. Patients ranged in age from 35 to 75 years (mean 55). Ectopic adrenal tissue was identified at the superior pole of the kidney in all but one case, which was located in the mid-portion of the kidney. Ectopic adrenal tissue varied in its growth from subcapsular lesions that were plaque-like (n=3), wedge-shaped (n=2), or spherical (n=1) to irregular nests deep in the renal parenchyma (n=1). In all nine cases, the adherent and intrarenal adrenal tissue was composed of adrenal cortical tissue, with no adrenal medullary tissue present. In six cases, adrenal tissue focally extended into renal parenchyma in an infiltrative manner. Of the nine cases, two were diagnostic problems for the contributing pathologists. In one case, intrarenal adrenal tissue mimicked low-grade clear cell renal cell carcinoma. In another case, an adrenocortical adenoma adherent to the kidney resembled renal invasion by adrenocortical carcinoma. This study summarizes key morphological features of intrarenal ectopic adrenal tissue and renal-adrenal fusion along with histological pitfalls and its differential diagnoses.