Massive mixed epithelial-stromal tumour of seminal vesicle requiring challenging abdominoperineal resection: a case report and review of literature.

Mixed epithelial-stromal tumours (MESTs) are a rare biphasic tumour that frequently arise in women from the renal and urogenital tract. They are also seen in men but are exceptionally uncommon with only few cases reported to originate from the seminal vesicles. Malignant transformation of its epithelial or stromal components is possible; however, by in large, these tumours are benign in nature. We report the case of a 48-year-old man with no remarkable medical or surgical history who presented with a huge expanding pelvic and intra-abdominal mass that required extensive surgical management including a pelvic exenteration. Histopathological analysis concluded the diagnosis of benign MEST originating from the seminal vesicles with no malignant features. No further systemic therapy was recommended for our patient. Given the technical intricacy in the operative resection of this tumour, we aim to present our findings and surgical management of this complex MEST.