Figure 3.

Immunohistochemical (IHC) findings of primary carcinoid tumor arising within mature teratoma of the kidney. (A) Cytokeratin 7 staining was positive in the urothelial-like epithelium, but negative in the carcinoid tumor cells and the colonic-like epithelium. Original magnification ×200. (B) Cytokeratin 20 staining was positive in the colonic-like epithelium, but negative in the carcinoid tumor cells and the urothelial-like epithelium. Original magnification ×400. (C) Synaptophysin staining was positive in the carcinoid tumor cells, but negative in the colonic-like epithelium and the urothelial-like epithelium. Original magnification ×200. (D) CD 56 staining was positive in the carcinoid tumor cells, but negative in the colonic-like epithelium and the urothelial-like epithelium. Original magnification ×200. (E) Both the colonic-like and urothelial-like epithelial lining of the teratomatous cystic spaces, and the carcinoid tumor cells showed positive pancytokeratin staining. Original magnification ×200. (F) Thyroxine staining was positive in the carcinoid tumor cells, but negative in the colonic-like epithelium and the urothelial-like epithelium. Original magnification ×200.