Ultrastructure of renal adenoma.

Renal adenomas, defined as minute cortical foci of proliferating epithelium, are frequently occurring lesions reported to be present in 15%-22% of all adult human kidneys. They can often be found in kidneys with renal cell carcinoma. Their light microscopic structure makes it improbable that they should represent intrarenal metastases. The concept does not include clear cell foci. Ultrastructure of these cortical foci in human kidneys is not well known. A series of 10 intrarenal adenomas in carcinoma-bearing kidneys has been studied using tissue fixed rapidly after nephrectomy by perfusion with 2% glutaraldehyde. The results confirm their tubular origin. Ultrastructural markers of different segments of the nephron were demonstrated. Several of these markers might be present in each single case. The interpretation is that their ultrastructural characteristics do not indicate an origin from a special segment of the nephron. They may reflect an abnormal gene expression associated with the neoplastic change of the cell clone. Some changes are similar to those seen in cells from renal cell carcinoma, although not as prominent as in malignant cells.