Figure 6.

Immunohistochemical (immunoperoxidase and hematoxylin counterstain) findings of synchronous primary carcinoid tumor and primary adenocarcinoma arising within mature cystic teratoma of horseshoe kidney. (A) CDX2 staining was positive in the mucinous columnar enteric-type or colonic-like epithelium lining of teratomatous cysts. Original magnification ×200. (B) Cytokeratin 20 staining was positive in the mucinous columnar enteric-type or colonic-like epithelium lining of teratomatous cysts. Original magnification ×200. (C) Smooth muscle actin was positive in teratomatous cyst wall. Original magnification ×200. (D) Cytokeratin 7 staining was positive in the adenocarcinoma component in right upper part of figure, but negative in the carcinoid tumor component in left lower part of figure. Original magnification ×200.