A small percentage of nephrogenic adenomas arise in renal transplant recepients. They most likely develop from renal tubular epithelial cells shed from the transplanted kidney. The immunoreactivity of nephrogenic adenomas for PAX2 and PAX8 markers (shown here) seems to support this hypothesis. PAX2 and PAX8 are transcription factors in the paired box (PAX) gene family. Both are expressed in normal renal tubular epithelium and in lesions derived from them.