Retroperitoneal Metastasis of a Primary Testicular Seminoma with Spontaneous Regression: A Case Report

Background: Spontaneous regression of testicular cancer with retroperitoneal metastasis is a rare phenomenon and poses challenges in its diagnosis. Methods: A 33-year-old male patient presented with severe lower back pain (10/10) of 4 months’ duration, radiating to the left lower limb, refractory to NSAIDs, and significantly impaired ambulation, accompanied by nausea and vomiting. In addition to difficulty initiating urination and defecation, with weight loss of 30 kg, he was referred to the urology service of our hospital. Results: On physical examination, the left testicle showed signs of varicocele without pain. Therefore, laboratory and imaging studies were requested, highlighting elevated β-hCG (156.4 mIU/mL) and LDH (850 IU/L). Testicular ultrasound confirmed the diagnosis of left varicocele, while computed tomography of the abdomen and pelvis with contrast revealed a conglomerated retroperitoneal mass of more than 5 cm, located in the paravertebral, retrocural, paraaortic, and intercavoaortic regions. Based on these findings, primary treatment with left radical orchiectomy was chosen, which showed regression of the seminomatous tumor. Histopathological examination revealed a seminomatous germ cell tumor (pT0, pN3, M0), clinical stage IIC, with a good prognosis. Therefore, chemotherapy was initiated with four cycles of EP (etoposide 170 mg and cisplatin 35 mg). However, despite standard chemotherapy, the disease progressed until the patient died. Conclusions: Cases of testicular tumor with retroperitoneal metastasis are rare and infrequently present with clinical, testicular, and imaging findings. Therefore, histopathology, accompanied by the intentional identification of mutations associated with the TP53 gene when therapeutic failure exists.