Generalized juvenile polyposis with mixed pattern and gastric cancer.

Generalized gastrointestinal juvenile polyposis is a rare form of diffuse polyposis in which cancer infrequently develops. A clinical case is described in which gastric polyps showed a variety of histological features, including both in situ and invasive adenocarcinoma. Many mixed lesions were observed, confirming a morphological sequence already documented in colorectal tumorigenesis but still undefined in gastric tumors. The patient seems strongly predisposed to gastric cancer, presumably on a genetic basis, because he developed a malignancy in a hyperplastic juvenile polyp, usually not considered a precancerous lesion. There is no doubt that cases like this may be important for accurate genetic evaluation and biological characterization.