Utility of p63 and high molecular weight cytokeratin in the distinction between urothelial carcinoma with prostatic stromal invasion and urothelial carcinoma with colonisation of prostatic ducts and acini

Aims: To evaluate the utility of p63 and high molecular weight cytokeratin in the distinction between urothelial carcinoma with prostatic stromal invasion and urothelial carcinoma with colonisation of prostatic ducts and acini which may be challenging on H&E, especially for general pathologists who may occasionally encounter these cases. Methods: A search of surgical pathology and consultation files was made for cystoprostatectomy specimens with confirmed urothelial carcinoma with prostatic stromal invasion. Intensity for both p63 and high molecular weight cytokeratin within the tumour cells were scored as negative/weak or strong. Results: A total of 34 cases were identified, 23 (68%) of which had associated foci of urothelial carcinoma with colonisation of prostatic ducts and acini. Mean patient age was 68.5 years (range 44-88 years). In all cases, basal cells of benign prostatic glands showed strong staining for both p63 and high molecular weight cytokeratin. Seventeen of 34 cases (50%) of urothelial carcinoma showed no or weak expression of high molecular weight cytokeratin in the tumour cells. The other 17 cases (50%) of urothelial carcinoma showed strong expression of high molecular weight cytokeratin in the tumour cells. Fourteen of 34 cases (41%) showed negative or weak expression of p63 in tumour cells. Twenty of 34 cases (59%) showed strong expression of p63 in tumour cells. In the 14 of 34 cases (41%) and 17 of 34 cases (50%) which showed negative/weak expression of p63 and high molecular weight cytokeratin, respectively, in the tumour cells, the positive staining of the basal cells by p63 and high molecular weight cytokeratin in the benign prostatic glands and acini or those colonised by urothelial carcinoma, aided in the distinction from urothelial carcinoma with prostatic stromal invasion. In the remaining 20 of 34 cases (59%) and 17 of 34 cases (50%) in which the tumour cells showed strong expression of p63 and high molecular weight cytokeratin, respectively, larger malignant tumour cells and smaller benign basal cells of the prostatic glands and acini were highlighted with these markers, and were easily distinguishable. Conclusion: Our study suggests that p63 and high molecular weight cytokeratin may be utilised in the distinction between urothelial carcinoma with prostatic stromal invasion and urothelial carcinoma with colonisation of prostatic ducts and acini.