Surgical resection of a PET-positive residual mass following curative-intent chemotherapy for a giant intra-abdominal seminoma: a case report

Giant intra-abdominal seminomas arising from cryptorchid testes are a rare clinical entity that presents significant diagnostic and therapeutic challenges. The management of substantial residual masses after first-line chemotherapy is particularly complex and often requires a multimodal approach. We report the case of a 41-year-old Asian man who presented with a massive retroperitoneal mass (15 × 23 cm) originating from a congenital undescended left testis. His serum β-hCG and LDH levels were markedly elevated. A CT-guided biopsy confirmed the diagnosis of a classical seminoma, and he was staged as having Stage IIIB disease. The patient was treated with four cycles of etoposide and cisplatin (EP) chemotherapy, achieving an excellent biochemical and radiological response. However, a significant residual mass (5.8 × 8.5 cm) with persistent low-grade metabolic activity on PET/CT (SUVmax 3.6) remained. Consequently, he underwent complete surgical resection of the residual lesion. Final histopathology revealed a complete pathological response with no viable malignant cells. At nearly 2 years of follow-up, the patient remains disease free with normal tumor markers. This case highlights the critical diagnostic role of surgical resection in selected patients with PET-positive residual masses following curative-intent chemotherapy for seminoma, providing definitive pathological clarification and guiding subsequent management.