Intrathyroid thymic carcinoma: report of two cases with pathologic and immunohistochemical studies.

Intrathyroid thymic carcinoma (ITCA) is a rare neoplasm of the thyroid gland, that is difficult to diagnose because of its complex pathologic and immunohistochemical characteristics. Here, we report two cases that may provide a better understanding of this disease. Case 1 is a 30-year-old man, and Case 2 is a 42-year-old man. The two cases showed an irregular solid thyroid mass on sonography. Histological examination revealed the solid growth of epithelial cells separated by bands of dense, hyalinized, and fibrous stroma. Tumor cells were positive for the expression of CD5, HMWK, CK19, CK5/6, CK7, EMA, CD117, p63, Bcl-2, and NANOG. It is noteworthy that the neuroendocrine markers Syn, NSE, and CgA were also observed. In Case 1, chemotherapy combined with radiotherapy, chest CT showed lung metastasis 4 months after resection. The patient was alive as of postoperative follow up lasting 46 months. Radical operation combined with radiotherapy was performed in case 2, and the patient was alive as of follow-up lasting 42 months.