COW-2021-21

1. d

1. Enteric-type/mucinous adenocarcinoma of prostatic urethra, moderately differentiated, involving prostatic tissue

In this prostate biopsy core, the tumor shows predominant cribriform architecture with minor acinar morphology, infiltrative growth in the prostatic stroma. Focal mucin producing with mucin pool formation is noted. Residual normal prostatic glands are in the background. The tumor involves right side of the prostate from apex to base (7 of 14 total biopsy cores, all from right side, spares left side of the prostate). Tumor length ranges from 1.5 mm to 11 mm microscopically. Morphologically it mimics conventional prostatic adenocarcinoma. NKX3.1 negativity raises red flag to call it conventional prostatic adenocarcinoma. This patient’s serum PSA is 0.9 ng/ml when prostate biopsy done, and his serum PSA was never elevated. But he had two TURP performed (2 years back and 2 months back) due to benign prostatic hypertrophy with urinary obstruction, and both showed enteric type adenocarcinoma with mucin producing and focal neuroendocrine differentiation. The earliest TURP (urologist saw glandular tissue in right lateral lobe with grey secretions and some gelatin like consistency) specimen showed tubulovillous adenoma with high grade dysplasia in prostatic urethra (Fig. 8), and invasive enteric type/mucinous adenocarcinoma. Besides two TURP, no other treatment was done except extensive GI work up which showed negative findings, arguing against metastasis from GI tract to the prostate. No lesion identified in urinary bladder endoscopically arguing against direct invasion from bladder. The current prostate biopsy is to evaluate the disease extent after recent TURP (2 months ago), then to make a decision for further management. The final diagnosis for this prostate biopsy is enteric type/mucinous adenocarcinoma of prostatic urethra involves prostatic tissue. Enteric type/mucinous adenocarcinoma of prostatic urethra was also called urothelial-type adenocarcinoma of the prostate before (reference 2).

Without knowing the history of this patient, the interpretation of this prostatic biopsy will be easily misinterpreted as conventional prostatic adenocarcinoma, with a Gleason score assigned. Especially without doubt about the cancer diagnosis, immunostains for either prostate triple or nkx3.1 will not attempt. Multiple immunostains were performed from the 1st TURP specimen to current prostate biopsy, the adenocarcinoma cells were consistently negative for NKX3.1, PSA+PAP, and CK7; positive for CK20 (Fig. 7), beta-catenin (membrane pattern), focally positive for CDX-2, SATB2, synaptophysin, and chromogranin A.

The treatment for enteric type/mucinous adenocarcinoma and conventional prostatic adenocarcinoma is different. Hormonal therapy (androgen deprivation) won’t be a choice for this patient with enteric type/mucinous adenocarcinoma. The patient refused to undergo radical prostatectomy. No distal metastasis developed since the diagnosis in past two years. Radiation therapy was offered to the patient recently.

Prostatic adenocarcinoma with mucinous features are definitely in differential diagnosis. The tumor cells should be positive for prostate markers (NKX3.1, PSA+PAP).

Enteric-type/mucinous adenocarcinoma directly invades to or metastatic to the prostate from urinary bladder and/or GI tract should be ruled out clinically. Morphologically and immunohistochemically are indistinguishable.

1. Osunkoya AO. Mucinous and secondary tumors of the prostate. Modern Pathology. 2018 Jan; 31:S80-S95 PMID: 29297488

2. Osunkoya AO, Epstein JI. Primary mucin-producing urothelial-type adenocarcinoma of prostate: report of 15 cases. Am J Surg Pathol 2007; 31:1323–1329 PMID: 17721186

Max Kong
Kaiser Sacramento Medical Center
Sacramento, CA, USA

Prostate

prostate; enteric-type adenocarcinoma; mucinous adenocarcinoma; prostatic urethra