A pure intertubular testicular seminoma mimicking a burned-out tumor: a case report

Background
In men presenting with metastatic seminoma and no discrete intratesticular mass, multiparametric MRI (mpMRI) findings such as atrophy, heterogeneity, calcifications, and focal low-signal areas are often interpreted as a regressed (“burned-out”) testicular primary. Rare non–mass-forming patterns, however, may produce similar indirect features and complicate primary-site attribution.

Case presentation

A 37-year-old man presented with abdominal pain and a 7-8-cm retroperitoneal mass; biopsy confirmed seminoma. Scrotal ultrasound demonstrated right testicular atrophy with diffuse parenchymal heterogeneity and a punctate calcification, without a focal lesion. Testicular mpMRI showed marked heterogeneity with a poorly defined subcapsular T2-hypointense pseudonodular area, heterogeneous enhancement with focal relative hypoperfusion, and regions of increased apparent diffusion coefficient—an appearance considered compatible with a burned-out tumor. Right inguinal orchiectomy performed prior to systemic therapy revealed diffuse viable seminoma with an exclusive intertubular growth pattern, associated germ cell neoplasia
in situ
, and prominent fibro-sclerotic remodeling, without a macroscopic mass. After three cycles of chemotherapy, the patient achieved a complete metabolic response.

Conclusion
This radiologic–pathologic correlation illustrates that diffuse viable intertubular seminoma with fibro-sclerotic remodeling can mimic burned-out tumor on mpMRI. In metastatic seminoma, subtle ipsilateral testicular abnormalities on ultrasound/mpMRI should prompt orchiectomy to secure definitive primary-site pathology and avoid misclassification as regression or extragonadal disease.