Comparison of the genetic alterations in two epithelial collision tumors of the uterine cervix. A report of two cases.

In a minority of cervical carcinomas, a distinct adenocarcinoma and squamous cell carcinoma component can be recognized. These tumors are considered collision tumors; the differential diagnosis is adenosquamous carcinoma. To investigate whether the squamous and adenocarcinoma component are of multiclonal or monoclonal origin, we used loss of heterozygosity (LOH) as a method to establish clonality. Each tumor component of two tumors with a distinct adenocarcinoma and squamous cell carcinoma component were microdissected and the presence of LOH was studied for nine chromosomes, i.e., 1, 2, 3, 6, 11, 15, 17, 18, and X, which are known to contain frequent LOH in cervical cancer. The tumor of patient AK13 showed identical LOH in both the adenocarcinoma and squamous cell carcinoma tissue with various microsatellite markers on chromosomes 1, 2, 6, 18, and X. For markers on chromosomes 3 and 15, different LOH patterns were found in both components. The squamous epithelium showed LOH on chromosome 3, whereas the adenocarcinoma component had LOH on chromosome 15. For patient AK18 the LOH pattern on chromosomes 6p and 17 was the same in the adenocarcinoma and the squamous cell carcinoma component. The adenocarcinoma component showed additional LOH on chromosomes 6q and chromosome 11q. The tumor of patient AK18 showed common boundaries of LOH in both components on chromosome 17q, between markers D17S578 and D17S250. In conclusion, the squamous cell carcinoma and adenocarcinoma components in both tumors most likely have one cell of origin because many genetic alterations are the same in each component. The presence of genetic changes uniquely associated with one of the tumors favors a diversion of developmental pathways.