Overexpression of c-kit protein is an infrequent event in small cell carcinomas of the uterine cervix.

Primary small cell carcinomas of the uterine cervix are uncommon but highly aggressive malignancies. The recent observations that c-kit proto-oncogene, a tyrosine kinase, is overexpressed in small cell lung cancers and that advanced c-kit-expressing gastrointestinal stromal tumors were successfully treated with a selective tyrosine kinase inhibitor STI-571 (Gleevec, imatinib mesylate) prompted us to investigate c-kit protein expression in cervical small cell carcinomas. Using a polyclonal antibody against c-kit protein (CD117), our immunohistochemical studies demonstrated a cytoplasmic staining in six of 22 cases (27%) of cervical small cell carcinoma. However, in five of these c-kit-positive cases, the immunoreactivity was focal and/or weak. Only one case (5%) exhibited a strong and diffuse staining pattern comparable to that seen in gastrointestinal stromal tumors. This was in contrast to small cell lung cancers where a positive staining for c-kit was observed in nine of 14 cases (64%) included in the study for comparison. Among them, five (36%) exhibited a strong and diffuse staining pattern. These results indicate that overexpression of c-kit protein is an infrequent event in small cell carcinomas of the uterine cervix. In comparison with small cell lung cancers, the findings presented in this report may reflect the difference in etiopathogenetic mechanisms underlying these two types of small cell carcinomas.