Pseudomalignant erosion in hyperplastic gastric polyps.

Six cases of hyperplastic gastric polyps are described that, in the region of the eroded head, revealed strikingly atypical mesenchymal cells. These disseminated cells with marked nuclear pleomorphism and also atypical mitotic figures, undergoing direct transition to typical granulation tissue, are considered to be particularly activated mesenchymal cells. In a single case in which only excisional biopsy was performed, these cells were found to persist over a lengthy period, while in endoscopic-biopsy follow-ups of the polypectomized cases, these cells were subsequently no longer detectable. In four of the cases, the polyp was located in the region of the cardia, so that a traumatic factor may possibly be considered as having some causal relevance. In particular when biopsy excisions are performed, the differential diagnosis of this polyp with its endoscopic and histologic appearance of a tumor-like lesion, from epithelial and mesenchymal malignancies, as also from neural tumors, can be difficult.