Histologic (hematoxylin and eosin stain) findings of synchronous primary carcinoid tumor and primary adenocarcinoma arising within mature cystic teratoma of horseshoe kidney. (A) Carcinoid tumor (left lower part of figure) and adenocarcinoma (right upper part of figure) components adjacent and closely apposed to each other without a clear transition zone. Original magnification ×100. (B) Carcinoid tumor showing the classical architectural pattern of trabecular nests of monotonous small round cells with peripheral palisading. Original magnification ×200. (C) Carcinoid tumor showing the classical architectural pattern of anastomosing ribbon-like nests of monotonous small round cells. Original magnification ×200. (D) Carcinoid tumor showing the classical cytologic features of fine granular "salt-and-pepper" chromatin pattern. Original magnification ×600.
Armah et al. Diagnostic Pathology 2009 4:17 doi:10.1186/1746-1596-4-17