The common 18-base pair deletion at codons 418-423 of the E-cadherin gene in differentiated-type adenocarcinomas and intramucosal precancerous lesions of the stomach with the features of gastric foveolar epithelium.

Alterations of the E (epithelial)-cadherin gene are often involved in undifferentiated-type carcinomas of the stomach, but not in the differentiated type. Recently, it was recognized that certain differentiated-type carcinomas possess the features of gastric foveolar epithelium. Such carcinomas are closely linked with undifferentiated-type carcinomas. Nineteen lesions (ten differentiated-type carcinomas and nine precancerous lesions) with a predominant gastric foveolar phenotype, as determined not only by mucin histochemistry and immunohistochemistry but also by morphology, were analysed for mutations of the E-cadherin gene using the nested polymerase chain reaction single-strand conformation polymorphism method. E-cadherin gene mutation was detected in 4 of 19 lesions (21 per cent) (three precancerous and one cancerous). Sequencing revealed an 18 bp deletion corresponding to codons 418-423 of exon 9 common to all four lesions. This mutation was previously reported in an advanced carcinoma of undifferentiated type. The results suggest that these tumours progress to undifferentiated-type carcinomas through loss of E-cadherin function. Copyright 1999 John Wiley & Sons, Ltd.