Retroperitoneal germ cell tumor, primary or secondary: A diagnostic conundrum

Germ cell tumor, seminoma, is the most common cancer in young men’s testis. However, a small subset of tumors (1%–2%) originate in other locations and are referred to as primary extragonadal germ cell tumors. But such type of tumors’ origin is thought to be controversial as a significant bulk may represent metastases from primary occult/regressed testicular germ cell tumors. The entire primary extragonadal germ cell tumor is mostly non-seminomatous and present in higher ages than primary testicular germ cell tumors, most of which are seminoma. A 50-year-old male presented with a brief history of abdominal pain for 10 days. Ultrasonography of his abdomen revealed multiple enlarged retroperitoneal lymph nodes. Biopsy and immunohistochemistry of the left iliac node showed features consistent with metastatic seminoma. Ultrasound of the left testis showed a hypoechoic lesion. Positron emission tomography scan showed increased tracer uptake in both the testes without any abnormal enhancing mass lesion and increased fluorodeoxyglucose uptake in the retroperitoneal lymph nodes. A high left inguinal orchidectomy revealed no tumor but a fibrotic scar tissue showing atrophic and ghost tubules, dense lymphoplasmacytic cells, and increased vascularity, implying regressed (burnt-out) seminoma. Regression of testicular seminoma shows a distinct constellation of findings permitting its diagnosis as a primary testicular tumor, which is imminent from a prognostic and therapeutic perspective.