PERITONEAL WASHING CYTOLOGY COMBINED WITH IMMUNOCYTOCHEMICAL STAININGAND DETECTING MUTANT K-RAS IN PANCREATIC-CANCER - COMPARISON OF THE SENSITIVITY AND AVAILABILITY OF VARIOUS METHODS

Peritoneal metastases are the second most common site of involvement, following the liver, in pancreatic cancer. Thus, we performed peritone al washing cytology at laparotomy to diagnose accurately the intraperi toneal spread of carcinoma cells to determine the appropriate therapy. Peritoneal washings were collected at laparotomy from 20 Japanese pan creatic carcinoma patients at Nagoya University Hospital between April 1993 and December 1994. From centrifuged deposits, we examined the cy tology by three methods as follows. The first method was conventional cytology, including May-Grunwald and Giemsa, Papanicolaou, periodic ac id-Schiff, and Alcian blue. The second method was immunocytochemical s taining, using antibodies to carbohydrate antigen (CA19-9) and carcino embryonic antigen. After extracting DNA from the remaining pellet, we studied the last method, detecting K-ras point mutation, by two-step p olymerase chain reaction and restriction fragment length polymorphism analysis. In two cases, peritoneal metastases were macroscopically rec ognized, and the results of all three methods were positive. In the tw o other cases, where peritoneal dissemination was not macroscopically recognized, the judgments of conventional cytological study and detect ing K-ras point mutation were negative. However, a few malignant cells were found by the immunocytochemical staining method. Judging from th eir clinical course, the positively stained cells were suggestive of m alignancy. At present, the immunocytochemical staining method is the m ost sensitive of these three methods in peritoneal washing cytology. H owever, preserving DNA is suitable for repeated examination, and a mod ified method can be applied. If the sensitivity increases, the method of detecting K-ras has the potential to become the standard for perito neal washing cytology in pancreatic cancer.