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Merkel cell carcinoma: evaluation of KIT (CD117) expression and failure to demonstrate activating mutations in the C‐KIT proto‐oncogene – implications for treatment with imatinib mesylate
Author(s) -
Swick Brian L.,
Ravdel Larisa,
Fitzpatrick James E.,
Robinson William A.
Publication year - 2007
Publication title -
journal of cutaneous pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 75
eISSN - 1600-0560
pISSN - 0303-6987
DOI - 10.1111/j.1600-0560.2006.00613.x
Subject(s) - cd117 , imatinib mesylate , merkel cell carcinoma , cancer research , exon , biology , gist , mutation , proto oncogene proteins c kit , tyrosine kinase inhibitor , tyrosine kinase , stromal cell , imatinib , pathology , cancer , gene , medicine , carcinoma , genetics , stem cell factor , receptor , stem cell , progenitor cell , cd34 , myeloid leukemia
Background: Merkel cell carcinomas (MCCs) express the tyrosine kinase receptor KIT. However, it is not known if MCCs have activating mutations in KIT that would make them responsive to treatment with imatinib mesylate. The purpose of this article is to describe the KIT immunohistological staining pattern (CD117) of MCCs and analyze those MCCs for mutations in areas of KIT where mutations are found in gastrointestinal stromal cell tumors. Methods: We evaluated KIT immunostaining in nine MCCs from nine patients. In addition, we extracted DNA from the same MCCs, performed PCR amplification of C‐KIT exons 9, 11, 13, and 17, and sequenced those gene products for mutations. Results: Eight of nine (88.8%) MCCs expressed KIT. No mutations were found. Conclusions: The majority of MCCs express KIT but do not contain activating mutations in exons 9, 11, 13, or 17 of KIT. Imatinib mesylate is unlikely to provide effective therapy in MCC unless activating mutations in other areas of KIT or activating mutations in other related genes can be detected.