Aims Pathological separation of poorly differentiated urothelial and prostate carcinoma is difficult, but imperative because of the impact on patient management. Tumour morphology, in conjunction with a panel of immunohistochemistry (IHC), such as prostate-specific antigen (PSA), prostatic acid phosphatase (PSAP), CK7, CK20, p63 and high molecular weight keratins (HMWKs) are usually employed to resolve this issue. Androgen receptor (AR) expression is maintained in high-grade, undifferentiated prostate carcinoma, and thus, could be considered as a potentially useful adjunct to the conventional panel of markers.
Methods We performed an institutional review of all cases from 2006 to 2012 in which AR IHC had been performed to determine its diagnostic utility in discriminating between poorly differentiated urothelial and prostate carcinoma. Of the eligible cases (n=40), there were 9 high-grade urothelial carcinomas, 27 prostate carcinomas and 4 with both prostate and bladder tumours. All diagnoses were made by integrating the clinical, radiological, morphological and IHC results.
Results In all the prostate carcinomas, there was diffuse, intense nuclear staining for AR. The urothelial tumours were either negative, had cytoplasmic staining or showed occasionally weak nuclear staining. The difference was highly significant with p<0.0001 (Mann–Whitney U test).
Conclusions We conclude that AR is an important marker as it is best able to distinguish between poorly differentiated urothelial and prostate carcinoma. AR appears superior to PSA and PSAP, which are not consistently expressed in high-grade prostate carcinoma. Also, high-grade urothelial carcinoma may be negative for CK20, p63/HMWK and occasionally CK7. We advocate the inclusion of AR in the panel of markers to differentiate these tumours.