Interphase fluorescence in situ hybridization studies of ovarian adenocarcinomas using the midisatellite probe

The genes involved in ovarian carcinogenesis are largely unknown. Cytogenetic studies have shown a large number of chromosomal abnormalities in ovarian cancers. Molecular studies have additionally found abnormalities. Few in situ hybridization studies have been performed on ovarian cancer tissues. We chose to study the distal region of chromosome 1p with the midisatellite probe and interphase fluorescence in situ hybridization. A total of 35 patient samples, including various controls and cancers, was collected from our pathology archives. Our cancer cases included some patients with stage I disease, in whom tumors arose in endometriotic cysts. In these cases, both tumor tissue and areas in the cyst distant from the tumor mass were examined. Results showed clear cell carcinoma nuclei to have an increase in both number and size of probe signals, interpreted as representing amplification of the probed region of chromosome 1. Serous carcinomas showed an increase in the number of signals, up to four. We felt this could be a result of amplification, or, because these cells exhibited the highest mitotic counts, to DNA doubling in preparation for mitosis. Endometrioid carcinomas resembled controls in showing up to two small probe signals, but not more. We conclude that amplification in distal chromosome 1p occurs in ovarian clear cell, and possibly serous, carcinomas and may not be important in endometrioid carcinomas. Because alteration was not found in the various control epithelia, including nonmalignant-looking areas from cysts which also contained cancer, we believe that the change, when present, may not be an early step in carcinogenesis.