Globular amyloid deposits in the wall of the gastrointestinal tract: report of six cases.

Amyloid deposition in the gastrointestinal tract basement membrane, lamina propria, and blood vessel walls has been well documented This article describes six cases that exhibited the unusual globular pattern of deposition on light microscopy, yet exhibited the classic histochemical and immunohistochemical properties of deposited amyloid This deposition pattern is a novel finding in the gastrointestinal system. Endoscopic examination of five patients revealed mild nodularity of the gastric mucosa and diffuse gastritis. In the other case, macroscopic examination of resected small intestine showed focal mucosal depressions. In all six cases, light microscopy study revealed round to oval-shaped globules in the lamina propria, with globule diameters of 3 to 40 microm. When stained with Congo red, the deposited material refracted polarised light, and immunohistochemical testing showed a positive reaction to AA antibody. The deposits did not react with antibodies to beta2 microglobulin, transthyretin, or lambda and kappa light-chain immunoglobulins. None of the laboratory or clinical findings in the six cases was compatible with monoclonal gammopathy or multiple myeloma. The literature contains a few case reports of globular amyloid deposition in the liver, but this is the first description of a globular pattern in the gastrointestinal tract. The pathogenesis and significance of this finding are not clear, and will require further study.