Abstract
Prostatic adenocarcinoma with focal pleomorphic giant cell features is rare with the only prior series consisting of 6 cases. From 2005 to 2018, we identified 29 cases from our consult service and 1 case from our own institution. Men ranged in age from 39 to 90 years (median = 75.5). Diagnostic specimens consisted of needle biopsies (n = 13); transurethral resections (n = 7), urethral/bladder biopsies (n = 8), radical prostatectomy (n = 1), and orchiectomy (n = 1). In all cases, there was usual acinar prostatic adenocarcinoma, where the highest grade in all cases was Gleason score 9 to 10 (Grade Group 5). On average, 68% of the involved cores had cancer with a maximum percent of cancer averaging 55%; on average, transurethral resections had 85% of the area involved by cancer. Areas of cancer showing pleomorphic giant cell features were focal (< 5%). Two of the needle biopsies showed extraprostatic extension. The radical prostatectomy had seminal vesicle invasion and positive margins with lymphovascular invasion. Prostatic adenocarcinoma with focal pleomorphic giant cell features is always accompanied by extensive usual acinar prostate adenocarcinoma where the highest grade in all cases was Gleason score 9 to 10 (Grade Group 5). Although the pleomorphic component is focal, it can mimic urothelial carcinoma. IHC can be misleading as PSA staining is often negative or focal in both the pleomorphic and usual prostatic adenocarcinoma components. NKX3.1 is the most sensitive prostate marker, but was still focal in 1 usual prostatic adenocarcinoma and negative in 2 pleomorphic components. Prostatic adenocarcinoma with focal pleomorphic giant cell features has a dismal prognosis. In men with no prior diagnosis of prostate adenocarcinoma and > 1-year follow-up, 7/19 (37%) were dead at a median of 8 months after diagnosis. Of the 7 men with a prior history of prostate adenocarcinoma, 4/7 (57%) were dead at a median of 7 months after diagnosis of recurrent prostate adenocarcinoma with pleomorphic giant cell features.