CD117, CK20, TTF-1, and DNA topoisomerase II-alpha antigen expression in small cell tumors.
BACKGROUND
Distinguishing merkel cell carcinoma (MCC), small cell lung carcinoma (SCLC) metastatic to the skin, and atypical basal cell carcinoma (BCC) can be problematic in some cases. Significant differences in the biology of these tumors necessitate that they need to be distinguished from one another.


METHODS
We evaluated the immunophenotypic characteristics of 22 MCCs, nine SCLCs, and 19 BCCs using antibodies to cytokeratin 20 (CK20), thyroid transcription factor-1 (TTF-1), CD117, and DNA topoisomerase II-alpha (topo II).


RESULTS
Nineteen of 22 MCCs stained with the antibody to CK20, none stained with anti-TTF-1, and 13 stained with anti-CD117. No SCLC stained with anti-CK20, all stained with anti-TTF-1, and eight stained with anti-CD117. No BCC stained with any of the three markers. The proliferative index (PI), determined by the expression of topo II, was similar for SLCLs (mean 58.5 +/- 9.0%) and MCCs (mean 45.2 +/- 12.4%) and was lowest in BCCs (mean 25.0 +/- 8.7%).


CONCLUSIONS
CK20 and TTF-1 appear to be reliable in distinguishing MCC from SCLC. CD117 is expressed in both MCC and SCLC, limiting its diagnostic utility. CK20, TTF-1, and CD117 are not expressed in BCC. The high PI seen in MCCs suggests a role for topoisomerase II inhibitors in their treatment.
Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA.
David T
DT
Yang
Joseph A
JA
Holden
Scott R
SR
Florell
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor / Q000032:analysis*; D002280:Basal Cell Carcinoma / Q000473:pathology*; D015266:Carcinoma, Merkel Cell / Q000378:metabolism / Q000473:pathology*; D018288:Carcinoma, Small Cell / Q000378:metabolism / Q000556:secondary*; D004250:DNA Topoisomerases, Type II / Q000096:biosynthesis; D004268:DNA-Binding Proteins; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D007381:Intermediate Filament Proteins / Q000096:biosynthesis; D053554:Keratin-20; D008175:Lung Neoplasms / Q000473:pathology*; D009687:Nuclear Proteins / Q000096:biosynthesis; D019009:Proto-Oncogene Proteins c-kit / Q000096:biosynthesis; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000096:biosynthesis
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; D007381:Intermediate Filament Proteins; C507499:KRT20 protein, human; D053554:Keratin-20; C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D019009:Proto-Oncogene Proteins c-kit; D004250:DNA Topoisomerases, Type II