by Jan Klos
Background
Cytokeratin 20 belongs to large family of cytokeratins (intermediate filaments with structural functions in the cell cytoplasm). It is an acidic keratin encoded on chromosome 17q with restricted distribution among the cells.
Staining in normal cells: enterocytes and goblet cells of gastrointestinal tract, umbrella cells in urothelium and Merkel cells in epidermis.
Staining in tumors: adenocarcinoma of small intestine, colon, rectum, appendix, enteric type carcinoma in lungs and sinonasal tract, urothelial carcinoma, urachal carcinoma, small cell carcinoma of salivary glands, Merkel cell carcinoma. Mucinous carcinoma ovary show diffuse staining in most of the cases. Focal reactivity is present in carcinomas of esophagus, stomach, biliary tract, pancreas, endometrioid and ovarian non-mucinous adenocarcinoma ……… Yolk sac tumor associated with a somatic epithelial neoplasm is positive in majority of cases.
Hepatoid adenocarcinoma, endocervical adenocarcinoma of gastric type, adenocarcinoma of salivary duct, cholangiocarcinoma …….. are positive in minority of cases. Neuroendocrine neoplasms other than Merkel cell carcinoma are rarely positive.
Staining pattern is cytoplasmic.
Control tissue: appendix or colon.
Application
- As a part of cytokeratin panel important in classification of carcinomas of unknown primary origin
- Subtyping of tumors
Selected references