Sources/Clones
American Research Products (IT-Ks 20.10, IT-Ks 20.3, IT-Ks 20.5), Biodesign, Cymbus Bioscience (Ks 20.8, Ks 20.3, Ks 20.5), Dako (K 20.8) and Progen (IT-Ks 20.3, IT-Ks 20.5, IT-Ks 20.8).
Fixation/Preparation
Formalin-fixed, paraffin-embedded tissue is ideally suited for this antibody. Immunoreactivity requires pretreatment with a sodium citrate buffer with heated antigen retrieval. Enzyme pretreatment (trypsin or pronase) should not be used as it abolishes signal. The antibody is not recommended for cryostat sections or cell smears due to crossreactivity with cytokeratin 20-epithelia.
Background
CK 20 is a low molecular weight cytokeratin, that was originally identified by Moll et al (1990) as protein IT in two-dimensional gel electrophoresis of cytoskeletal extracts of intestinal epithelia. The antibody reacts with the 46 kD cytokeratin intermediate filament isolated from villi of duodenal mucosa. CK 20 is less acidic than other type 1 cytokeratins and is particularly interesting because of its restricted range of expression.
In normal tissues it is expressed only in gastrointestinal epithelium, urothelium and Merkel cell. Other epithelial cells, including breast epithelia, do not react with CD20, nor does it recognize other intermediate filament proteins.
Applications
Following extensive testing on both primary and metastatic carcinomas, it was concluded that tumors expressing CK 20 were derived from normal epithelia expressing CK 20 (Moll et al, 1992). Hence, colorectal carcinomas consistently express CK 20 while gastric adenocarcinomas and other carcinomas of the gastrointestinal tract express this cytokeratin isotype less frequently. In addition, adenocarcinomas of the biliary tree and pancreatic duct, mucinous ovarian tumors and transitional cell carcinomas also demonstrate positive immunoreaction. Hence, the application of CK 20 antibody for determining the site of origin of carcinomas has been recently mooted largely due to absence of CK 20 expression in adenocarcinomas of the breast, lung, endometrium and nonmucinous tumors of the ovary (Appendices 1.13, 1.19, 1.28). In fact, CK 20 has recently contributed to immunohistochemical evidence supporting the appendiceal origin of pseudomyxoma peritonei in women (Ronnett et al, 1997).
Immunostaining for CK 7 and CK 20 has been shown to be useful in the differentiation of ovarian metastases from colonic carcinoma and primary ovarian carcinoma (Loy et al, 1996). A CK 7-/CK 20+ immunophenotype was seen in 94% of metastatic colonic carcinomas to the ovary, 5% of primary ovarian mucinous carcinomas and none of the primary ovarian endometrioid or serous carcinomas.
The almost consistent staining of Merkel cell carcinoma for CK 20 and the very low frequency of CK 20 reactivity in other small cell carcinomas (except those of salivary gland origin) can help to resolve the diagnostic dilemma between Merkel cell carcinoma and metastatic small cell carcinoma presenting in the skin (Chan et al, 1997) (Appendix 1.19). In fact, it was recently shown that CK 20 positivity in a small cell carcinoma of uncertain origin is strongly predictive of Merkel cell carcinoma, especially when the majority of tumor cells are positive. In contrast, a negative
CK 20 reaction practically rules out Merkel cell carcinoma, provided an effective antigen retrieval technique is used and appropriate immunoreaction obtained with other cytokeratin antibodies.
Finally, CK 20 positivity is often encountered in transitional cell carcinomas of the bladder but is rare in squamous carcinomas of that organ or adenocarcinoma of prostate (Moll et al, 1992).
Comments
CK 20 works extremely well in paraffin sections with microwave antigen retrieval in citrate buffer. It is extremely useful for the distinction between colonic and non-mucinous ovarian adenocarcinomas. Identifying Merkel cell carcinoma from metastatic small cell carcinoma to the skin is also easily accomplished with CK 20. Colonic carcinoma tissue sections should be used as positive control tissue.
References
•Chan JKC, Suster S, Wenig BM et al 1997. Cytokeratin 20 immunoreactivity distinguishes Merkel cell (primary cutaneous neuroendocrine) carcinomas and salivary gland small cell carcinomas from small cell carcinomas of various sites. American Journal of Surgical Pathology 21: 226-234.
•Loy TS, Calaluce RD, Keeney GL 1996. Cytokeratin immunostaining in differentiating primary ovarian carcinoma from metastatic colonic adenocarcinoma. Modern Pathology 9: 1040-1044.
•Moll R, Schiller DL, Franke WW 1990. Identification of protein IT of the intestinal cytokeratin as a novel type I cytokeratin with unusual properties and expression patterns. Journal of Cell Biology 111: 567-580.
•Moll R, Lçe A, Laufer J, Franke WW 1992. Cytokeratin 20 in human carcinomas. A new histodiagnostic marker detected by monoclonal antibodies. American Journal of Pathology 140: 427-447.
•Ronnett BM, Shmookler BM, Diener-West M, Sugarbaker PH, Kurman RJ 1997. Immunohistochemical evidence supporting the appendiceal origin of pseudomyxoma peritonei in women. International Journal of Gynecologic Pathology 16: 1-9.
Bibliografía
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
American Research Products (IT-Ks 20.10, IT-Ks 20.3, IT-Ks 20.5), Biodesign, Cymbus Bioscience (Ks 20.8, Ks 20.3, Ks 20.5), Dako (K 20.8) and Progen (IT-Ks 20.3, IT-Ks 20.5, IT-Ks 20.8).
Fixation/Preparation
Formalin-fixed, paraffin-embedded tissue is ideally suited for this antibody. Immunoreactivity requires pretreatment with a sodium citrate buffer with heated antigen retrieval. Enzyme pretreatment (trypsin or pronase) should not be used as it abolishes signal. The antibody is not recommended for cryostat sections or cell smears due to crossreactivity with cytokeratin 20-epithelia.
Background
CK 20 is a low molecular weight cytokeratin, that was originally identified by Moll et al (1990) as protein IT in two-dimensional gel electrophoresis of cytoskeletal extracts of intestinal epithelia. The antibody reacts with the 46 kD cytokeratin intermediate filament isolated from villi of duodenal mucosa. CK 20 is less acidic than other type 1 cytokeratins and is particularly interesting because of its restricted range of expression.
In normal tissues it is expressed only in gastrointestinal epithelium, urothelium and Merkel cell. Other epithelial cells, including breast epithelia, do not react with CD20, nor does it recognize other intermediate filament proteins.
Applications
Following extensive testing on both primary and metastatic carcinomas, it was concluded that tumors expressing CK 20 were derived from normal epithelia expressing CK 20 (Moll et al, 1992). Hence, colorectal carcinomas consistently express CK 20 while gastric adenocarcinomas and other carcinomas of the gastrointestinal tract express this cytokeratin isotype less frequently. In addition, adenocarcinomas of the biliary tree and pancreatic duct, mucinous ovarian tumors and transitional cell carcinomas also demonstrate positive immunoreaction. Hence, the application of CK 20 antibody for determining the site of origin of carcinomas has been recently mooted largely due to absence of CK 20 expression in adenocarcinomas of the breast, lung, endometrium and nonmucinous tumors of the ovary (Appendices 1.13, 1.19, 1.28). In fact, CK 20 has recently contributed to immunohistochemical evidence supporting the appendiceal origin of pseudomyxoma peritonei in women (Ronnett et al, 1997).
Immunostaining for CK 7 and CK 20 has been shown to be useful in the differentiation of ovarian metastases from colonic carcinoma and primary ovarian carcinoma (Loy et al, 1996). A CK 7-/CK 20+ immunophenotype was seen in 94% of metastatic colonic carcinomas to the ovary, 5% of primary ovarian mucinous carcinomas and none of the primary ovarian endometrioid or serous carcinomas.
The almost consistent staining of Merkel cell carcinoma for CK 20 and the very low frequency of CK 20 reactivity in other small cell carcinomas (except those of salivary gland origin) can help to resolve the diagnostic dilemma between Merkel cell carcinoma and metastatic small cell carcinoma presenting in the skin (Chan et al, 1997) (Appendix 1.19). In fact, it was recently shown that CK 20 positivity in a small cell carcinoma of uncertain origin is strongly predictive of Merkel cell carcinoma, especially when the majority of tumor cells are positive. In contrast, a negative
CK 20 reaction practically rules out Merkel cell carcinoma, provided an effective antigen retrieval technique is used and appropriate immunoreaction obtained with other cytokeratin antibodies.
Finally, CK 20 positivity is often encountered in transitional cell carcinomas of the bladder but is rare in squamous carcinomas of that organ or adenocarcinoma of prostate (Moll et al, 1992).
Comments
CK 20 works extremely well in paraffin sections with microwave antigen retrieval in citrate buffer. It is extremely useful for the distinction between colonic and non-mucinous ovarian adenocarcinomas. Identifying Merkel cell carcinoma from metastatic small cell carcinoma to the skin is also easily accomplished with CK 20. Colonic carcinoma tissue sections should be used as positive control tissue.
References
•Chan JKC, Suster S, Wenig BM et al 1997. Cytokeratin 20 immunoreactivity distinguishes Merkel cell (primary cutaneous neuroendocrine) carcinomas and salivary gland small cell carcinomas from small cell carcinomas of various sites. American Journal of Surgical Pathology 21: 226-234.
•Loy TS, Calaluce RD, Keeney GL 1996. Cytokeratin immunostaining in differentiating primary ovarian carcinoma from metastatic colonic adenocarcinoma. Modern Pathology 9: 1040-1044.
•Moll R, Schiller DL, Franke WW 1990. Identification of protein IT of the intestinal cytokeratin as a novel type I cytokeratin with unusual properties and expression patterns. Journal of Cell Biology 111: 567-580.
•Moll R, Lçe A, Laufer J, Franke WW 1992. Cytokeratin 20 in human carcinomas. A new histodiagnostic marker detected by monoclonal antibodies. American Journal of Pathology 140: 427-447.
•Ronnett BM, Shmookler BM, Diener-West M, Sugarbaker PH, Kurman RJ 1997. Immunohistochemical evidence supporting the appendiceal origin of pseudomyxoma peritonei in women. International Journal of Gynecologic Pathology 16: 1-9.
Bibliografía
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
