Papillary Thyroid Cancer in Struma Testis with Malignant Transformation in the Lung Associated with Trisomy 17 Successfully Treated with Total Thyroidectomy and Radioiodine Ablation

BACKGROUND Struma testis is a rare entity, and there are only few reports on the malignant transformation of a testicular teratoma to papillary thyroid carcinoma in the literature. In this report, we describe the malignant transformation of struma testis with distant lung metastasis associated with trisomy 17 and a coexisting papillary microcarcinoma in the thyroid. CASE REPORT A 56-year-old man presented after a left orchiectomy for an undescended left testicle. Pathologic examination identified a monodermal teratoma composed of thyroid parenchyma and associated with a 1.7-cm papillary thyroid carcinoma. Further evaluation showed a pulmonary mass on a chest CT scan. Total thyroidectomy revealed a 0.5-mm focus of papillary thyroid cancer, and removal of the lung mass confirmed metastatic papillary thyroid cancer. Array-comparative genomic hybridization of both tumors showed trisomy 17 in the struma testes and the lung metastasis. The patient responded well to radioactive iodine ablation and has no evidence of cancer 3 years later. CONCLUSION To our knowledge, this is the first case of papillary thyroid cancer in struma testes metastatic to the lung. It highlights the difficulties in treating these patients. Surgery to remove cancer foci, followed by radioactive iodine ablation, resulted in an excellent response in our patient. Interestingly, trisomy 17, which has so far been observed only in noninvasive thyroid nodules, was associated with pulmonary metastasis in our patient.