2019-12 / MAY 6

A 70 year old man underwent a 12 part needle biopsy of the prostate due to elevated serum PSA levels. In one part, an atypical focus at the end of the needle biopsy was noted.


What is the correct diagnosis?

a. Adenocarcinoma of the prostate, Gleason score 3+3=6 (Grade Group 1)

b. Adenocarcinoma of the prostate, Gleason score 3+4=7 (Grade Group 2)

c. Atypical glands, suspicious for adenocarcinoma

d. Nephrogenic adenoma

Nephrogenic adenoma

Histologically, at the end of the core is a small cluster of crowded glands associated with calcifications. The glands are small and atrophic. Focally, there is a papillary frond (best seen on the PIN4 stain). The cells lining the glands and frond are cuboidal or flattened with some having intraluminal blue-tinged mucinous secretions. Nucleoli are visible. Prostate adenocarcinoma typically does not have such an atrophic appearance and would not have a papillary component. The PIN4 stain shows an absence of p63 with some faint labeling of the lesion with high molecular weight cytokeratin. AMACR is strongly positive. If this lesion was on a bladder biopsy, the first thought would have been nephrogenic adenoma, but this lesion is rarely sampled on a prostate needle biopsy. Given its morphology, stains were performed for PAX8 which was positive and was negative for NKX3.1, confirming the diagnosis of nephrogenic adenoma. Nephrogenic adenomas not infrequently are negative for p63 and HMWCK and are typically positive for AMACR such that the stains can be misleading for prostate adenocarcinoma.

Benign Mimickers of Prostate Adenocarcinoma on Needle Biopsy and Transurethral Resection. Netto GJ, Epstein JI.
Surg Pathol Clin. 2008 Dec;1(1):1-41.

Jonathan Epstein
Johns Hopkins Hospital


nephrogenic adenoma