LAUSR

Primary seminal vesicle adenocarcinoma is a rare malignancy of the male genito‐urinary system with only a few confirmed reported cases. Initial tissue diagnostic modality is often a core biopsy specimen. Here, we report this rare entity in a 50‐year‐old male, highlighting the histomorphological and immunohistochemical approach to the core biopsy specimen of the seminal vesicle mass. The patient presented with a history of haematospermia and gross haematuria for one year, and radiological workup was found to have a right seminal vesicle mass. A trans‐rectal ultrasound guided core biopsy revealed a tumourous lesion with a predominant papillary architecture and cytological features of neoplasia. Based on positivity for CK7, PAX‐8 and CA‐125, and Ki‐67 index of 30%–40% and negativity for PSA, AMACR, CK20, CDX‐2, p63, GATA3, WT1 and calretinin, a diagnosis of primary seminal vesicle adenocarcinoma was offered. The diagnosis was also confirmed on the surgically resected specimen. This case depicts the approach of a pathologist to diagnose this rare entity on the core biopsy specimen and the possible differential diagnoses one must consider.