Two patients with metastasis of cancer to other neoplasm: A thyroid carcinoma metastatic to a lung carcinoma and a gastric carcinoma metastatic to a thyroid adenoma.

Two patients with rare cancer-to-neopiasm metastasis are presented. One patient was a 69-year-old woman who had undergone gastrectomy for gastric cancer 10 months previously and died of generalized metastases. An autopsy revealed generalized metastases of the gastric carcinoma, together with a cystic, hemorrhagic thyroid tumor measuring 2.0 cm in diameter. Histologically, the thyroid tumor was an oxyphilic adenoma with multiple metastatic foci of gastric adenocarcinoma. Because no metastasis was found in the background thyroid tissue, this metastasis might have developed specifically and not by chance, most likely due to the rich vascularity and good circulation of the thyroid adenoma. The other patient was an 82-year-old man who had undergone total thyroidectomy for thyroid cancer 6 years previously. An abnormal lung shadow was found on a chest radiograph during postoperative follow-up. Transbronchial biopsy of the lung tumor revealed a squamous-cell carcinoma. The resected lung tumor measured 2.7 cm in diameter, with small foci of metastatic papillary carcinoma of the thyroid gland and multiple small metastases in the background lung tissue, indicating that the metastases to lung cancer had occurred by chance. Metastasis of cancer to other neoplasms is discussed, and a review of the literature is presented.