Primary seminal vesicle adenocarcinoma: A case report of rare entity and discussion of its differential diagnosis using immunohistochemical approach for the core biopsy specimen

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.