Mucinous adenocarcinoma of Prostate (MAOP), a rare variant of prostate adenocarcinoma: a case report and literature review

Abstract

A prostatectomy specimen was received from a 72-year-old male with a previous needle core biopsy diagnosis of prostatic adenocarcinoma, Gleason score 3+4=7. Microscopic examination of the prostatectomy specimen demonstrated single and fused neoplastic glands floating in copious amounts of extracellular mucin representing >50% of the tumour volume. There was a minor component of non-mucinous conventional adenocarcinoma in the background. Immunhistochemistry NKX 3.1 and PSA showed positive staining of tumour cells. Clinical, radiological or serological evidence of carcinoma of another site was not revealed. A diagnosis of MAOP, Gleason score 4+3 =7 (WHO/ISUP Grade Group 3) with a tertiary component of Gleason pattern 5 comprising <1% of total tumour volume was made. MAOP is a rare variant, comprising 0.38–0.43% of prostatic carcinoma. It is characterised by tumour cells floating in >25% of extracellular mucin excluding any intraluminal mucin. The diagnosis should only be made in resection specimens, and following exclusion of secondary deposits of extra-prostatic origin of mucinous adenocarcinoma by clinical-radiological correlation and with confirmatory immunohistochemistry. Grading and scoring for MAOP should be performed according to the growth pattern similar to conventional adenocarcinoma. The prognosis appears to be similar to non-mucinous prostatic adenocarcinoma.