Plasmacytoid acinar adenocarcinoma of the prostate: a newly described variant of prostate cancer.

A plasmacytoid variant of prostatic adenocarcinoma has not been reported to the best of our knowledge. A 54-year-old male presented with recurrent attacks of acute urinary retention. Laboratory findings showed high creatinine and a serum prostate specific antigen of 50.7 μg/L. Magnetic Resonance Imaging showed a locally advanced tumor involving the bladder and extending to the base of prostate with bilateral ureterovesical junction involvement and invasion of the left seminal vesicle and left anterior mesorectal fascia as well as perirectal fat invasion. Diffuse metastases to the abdominopelvic lymph nodes were identified. Bone scintigraphy showed multiple bone metastases. Transrectal ultrasound guided biopsy of the prostate was attempted but the patient could not tolerate the procedure and the procedure was canceled. The patient then underwent transurethral resection of bladder tumor. Microscopic examination showed sheets of malignant cells with prominent plasmacytoid appearance undermining benign urothelium. The tumor cells were positive for PSA, PSAP, NKX 3.1 and Cytokeratin 8/18. The tumor cells were negative for P63, Cytokeratin 34βE12, Cytokeratin 20, Desmin, CD38, Kappa and Lambda light chains, Chromogranin, Synaptophysin, GATA 3, E-cadherin and CD45. INI1 was retained. Next generation sequencing showed an intermediate tumor mutational burden. Notably, no genomic alterations in the CDH1 gene (encoding for E-cadherin) were present. The patient showed some initial response to antiandrogen therapy with a drop in serum PSA levels following androgen deprivation therapy. However, the patient died 6 months after diagnosis. It is critical to recognize this newly described variant and to distinguish it from plasmacytoid urothelial carcinoma. Recognition of the newly described plasmacytoid variant of adenocarcinoma of the prostate will lead to identification and reporting of more cases and a better understanding of its clinicopathologic features.