Squamous metaplasia of the peritoneum. The capacity of the peritoneal serosa to undergo metaplasia to mullerian-type epithelium is well recognized. We report a case of squamous metaplasia of the peritoneum that was studied by light microscopy. Immunohistochemical techniques, and electron microscopy. The pathogenesis of peritoneal squamous metaplasia is obscure, but may be a response to chronic irritation. 