P53 PROTEIN OVEREXPRESSION IN GALLBLADDER CARCINOMA AND ITS PRECURSORLESIONS - AN IMMUNOHISTOCHEMICAL STUDY

Gallbladder carcinoma is one of the most frequent neoplasms diagnosed in Chile. Although the premalignant lesions have been extensively stud ied and are well characterized, there is only limited information abou t the genetic abnormalities that might be important in the pathogenesi s of gallbladder carcinoma or that might have prognostic implications. The present study evaluates the immunohistochemical expression of p53 protein in premalignant lesions and invasive carcinoma of the gallbla dder, and correlates the p53 expression with histological type, grade of differentiation, and level of invasion of the tumor. The authors st udied the immunohistochemical p53 protein overexpression in 52 gallbla dder carcinomas, 47 carcinomas in situ (CISs), 34 dysplasias, and 10 s pecimens with chronic cholecystitis containing normal and metaplastic epithelium. A semiquantitative scoring system was used to assess the p 53 reactivity. p53 overexpression was found in 34 of 52 (65.4%) carcin omas, 21 of 47 (44.7%) CISs, and 11 of 34 (32.4%) dysplasias. There we re no significant differences in p53 expression in premalignant lesion s associated with invasive carcinoma and those that were not, Normal a nd metaplastic epithelium did not overexpress p53 protein. In adenocar cinomas, no correlation was found between p53 protein overexpression a nd histological subtype, grade of differentiation, or level of invasio n. The high incidence of p53 overexpression in gallbladder carcinoma a nd its presence in dysplasia, even in specimens without invasive carci nomas, suggests that this abnormality is an important and early event in the pathogenesis of the tumor, The progressively increasing inciden ce of p53 overexpression observed from premalignant lesions to invasiv e tumor provides additional support to the view that this is the usual route for the development of infiltrating gallbladder carcinoma. (C) 1996 by W.B. Saunders Company