Primary Extra-Gonadal Retroperitoneal Seminoma, Clinically Mimicking Sarcoma.

Extra-gonadal Germ cell tumours (EGCTs) are germ cell tumours that are found in locations other than the gonads. These tumours are seen in young males in the midline, mostly in the mediastinum followed by retroperitoneum, pineal gland, and sacrococcygeal area. While most of these are non-seminomatous, few are seminomatous. We present here a case report of a 25-year-old, mentally retarded male patient, with bilaterally normal testes, who presented with a huge mass in abdomen. The ultrasound and CECT (Contrast Enhanced Computerized Tomography) scan done showed two large retroperitoneal masses, which on FNAC (Fine Needle Aspiration Cytology) suggested germ cell tumour. Surgical resection was done and the subsequent histopathological examination provided the diagnosis of seminoma, which was further confirmed by PAS (Periodic Acid Schiff) staining and Immunohistochemistry for PLAP (Placental Alkaline Phosphatase). Retroperitoneum is a common site for sarcomas, which also present as huge, bulky masses. Thus, EGCTs should be considered in the differential diagnosis of a soft-tissue mass in abdomen, especially arising in the retroperitoneum.