130 Growing Teratoma Syndrome: A Rare Phenomenon

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Introduction/Objective Growing teratoma syndrome (GTS) is a rare entity occurring in approximately 1.9–7.6% of patients with testicular non-seminomatous germ cell tumors (NSGCTs). It is characterized by a paradoxical increase in metastatic mass size during or after chemotherapy despite normalization of serum tumor marker levels. Early recognition is crucial, as surgical excision is curative and prevents unnecessary additional therapy. Methods/Case Report We report a 30-year-old male presenting with waxing and waning left upper quadrant abdominal pain and weight loss following right orchiectomy for a mixed germ cell tumor (embryonal carcinoma 40%, yolk sac tumor 10%, and teratoma 50%). Post-chemotherapy, serum tumor markers normalized except for mildly elevated AFP. Results Contrast-enhanced CT demonstrated a heterogeneous mass in the left hepatic lobe, a complex mesenteric mass, and mesenteric lymphadenopathy. The patient underwent partial hepatectomy, intra-abdominal tumor excision, retroperitoneal lymphadenectomy, and appendectomy. Histopathologic examination confirmed mature teratoma consistent with GTS. The patient remained disease-free at three-month follow-up. Conclusion GTS should be suspected in patients with non-seminomatous germ cell tumors who develop enlarging masses after chemotherapy despite normalized tumor markers. Accurate diagnosis is critical to avoid misinterpretation as disease progression. Complete surgical excision offers an excellent prognosis, as GTS is unresponsive to chemotherapy and radiotherapy.