SMOOTH-MUSCLE TUMORS OF THE GASTROINTESTINAL-TRACT - EXPRESSION OF RAS P21 ONCOGENE PRODUCT AND THE ASSOCIATION WITH CLINICOPATHOLOGY

Quantitative analysis of ras oncogene product P21 was performed on par affin blocks from 55 smooth muscle tumors of the gastrointestinal trac t by immunofluorescence and flow cytometry, No positive evidence for P 21 was found in 5 caries of normal smooth muscle tissues. Eight of 14 leiomyomas were P21 positive (57%) but all of them were tower expresse d with fluorescence index (FI) <1.25, whereas a total of 29 leiomyosar comas and 12 potential malignant smooth muscle tumors were found to be P21 positive (100%), and the majority were overexpressed with FI>1.25 (P<0.005). ras P21 was overexpressed significantly in the tumors with mitotic counts of more than 1/10 high power field (P<0.005). It was a lso overexpressed significantly as soon as the mild cytologic atypia o f the tumor was found (P<0.005). Five-year survival rate was significa ntly higher in the patients with lower-expression of ras P21 than thos e with overexpression (P<0.005). It was suggested that the expression of ras oncogene product P21 could be used as an objective parameter in distinguishing malignants from benigns and predicting the prognosis o f the patients with smooth muscle tumors of the gastrointestinal tract .