Apparent Histologic Discordance in Recurrent Testicular Germ Cell Tumor With Bulky Retroperitoneal Disease and Inferior Vena Cava Compression: A Case Report and Brief Review of the Literature.

Testicular germ cell tumors are highly curable, but bulky retroperitoneal recurrence creates diagnostic uncertainty when a limited biopsy does not capture all components of the primary tumor. A 35-year-old man presented with abdominal pain radiating to the back and intermittent constipation nearly five years after an orchiectomy for a 6.5-cm mixed germ cell tumor consisting of seminoma (80%) and embryonal carcinoma (20%) with lymphovascular invasion. CT showed a heterogeneous 14.1-cm retroperitoneal nodal mass with near-complete inferior vena cava effacement. Retrospective comparison with prior imaging identified a 2.1-cm focus at the same site on a June 2022 study; no intervening imaging was available. Lactate dehydrogenase (LDH) was 630 U/L (2.25 times the upper limit of normal), beta-human chorionic gonadotropin (β-hCG) was minimally elevated, and alpha-fetoprotein (AFP) was normal. A core biopsy showed seminoma with focal necrosis; no nonseminomatous component was identified in the sampled tissue. With the pulmonary micronodules regarded as indeterminate rather than metastatic, the available data were consistent with cN3 cM0 S2, stage IIIB. Because the primary tumor contained embryonal carcinoma and because core sampling could not exclude unsampled nonseminoma, the oncology team applied an intermediate-risk nonseminomatous germ cell tumor framework and initiated curative-intent bleomycin, etoposide, and cisplatin, with four cycles planned. At the last available follow-up, the patient had completed the inpatient portion of cycle 1 without major acute toxicity and reported improved pain; neither treatment completion nor radiographic response was available. Apparent histologic discordance on core biopsy should be interpreted in light of the original pathology, serum markers, imaging, and multidisciplinary assessment.