A 22-year-old man presents with chest pain and dry cough. CT chest reveals a 9 cm anterior mediastinal mass with fat, fluid, and calcification. The structure marked **B** in the diagram is identified on gross specimen examination. Serum α-fetoprotein and β-hCG are normal. Histopathology demonstrates well-differentiated derivatives of ectoderm, mesoderm, and endoderm without immature elements. Which of the following is the most appropriate next step in management?
A. Testicular ultrasound followed by chemotherapy if primary identified
B. Radiation therapy to the anterior mediastinum
C. Cisplatin-based chemotherapy (BEP regimen)
D. Surgical excision via median sternotomy followed by observation
Explanation
Why Surgical excision via median sternotomy followed by observation is right
The tooth-like calcification marked B, combined with normal tumor markers (AFP, β-hCG), histology showing well-differentiated derivatives of all three germ layers without immature elements, and the clinical presentation of a 9 cm anterior mediastinal mass, is pathognomonic for a mature cystic teratoma. According to Sabiston 21e and WHO Thoracic Tumors 5e, mature teratomas are benign lesions (60–70% of mediastinal germ cell tumors) and surgical excision is curative. No adjuvant chemotherapy or radiation is required for fully resected mature teratoma, making observation after complete surgical resection the standard of care.
Why each distractor is wrong
Cisplatin-based chemotherapy (BEP regimen): BEP is reserved for seminomas and non-seminomatous germ cell tumors with elevated tumor markers. Normal AFP and β-hCG exclude these diagnoses and indicate a mature teratoma, which does not require chemotherapy after complete excision.
Radiation therapy to the anterior mediastinum: Radiation is not indicated for mature teratomas. It may be considered for seminomas (which are radiosensitive) or for residual disease in non-seminomatous tumors, but the normal markers and benign histology here exclude those diagnoses.
Testicular ultrasound followed by chemotherapy if primary identified: While testicular ultrasound is part of the workup to exclude an occult primary gonadal tumor, it is performed at diagnosis, not after histologic confirmation of a mature teratoma. The normal markers and mature histology already exclude a primary testicular malignancy requiring chemotherapy.
High-YieldNEET PG
Mature mediastinal teratoma + normal AFP/β-hCG + well-differentiated histology = surgical excision alone is curative; no chemotherapy needed.
Sabiston 21e Ch 58 Mediastinum; WHO Thoracic Tumors 5e
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