Russell Body Gastritis: Histochemical and Immunohistochemical Findings in a Series of Three Patients.

Russell body gastritis is a discrete morphologic pattern of chronic gastritis, characterized by numerous plasma cells filled with intracytoplasmic Russell body inclusions. It can be mistaken for neoplastic lesions and for extracellular hyaline structures. We report three adult men with Russell body gastritis. The patients were diagnosed and treated for various hematolymphoid disorders. During follow-up, they presented with abdominal pain, gastric erythema and thickening. One patient had Helicobacter pylori infection. The gastric biopsy showed an expanded lamina propria filled with numerous plasma cells containing hyaline glassy globules. Initial hematoxylin and eosin impression included amyloidosis, gastric antral vascular ectasia, neuroendocrine tumor, plasma cell neoplasm and low-grade lymphoma with plasmacytic features. The inclusions showed a homogenous magenta staining pattern with periodic acid-Schiff and diastase, a central dark red core surrounded by a bluish ring with Masson trichrome, and were apple-green with mucicarmine. Although they showed an orangeophilic amyloid-like staining pattern with Congo red, they were not birefringent. The inclusions were metachromatic and nested in clefted lacunar spaces. The plasmacytoid and rhabdoid cells expressed CD45, CD38, CD138, CD79a and epithelial membrane antigen. They were polytypic with kappa and lambda light chains. The immunomarkers showed a characteristic reticulated network surrounding the inclusions, creating a negative image. Russell body gastritis is a rare and special form of chronic gastritis. It can be mistaken for various lesions. Histochemical and immunohistochemical stains are useful ancillary diagnostic tools. The occurrence of this phenomenon in certain patients with compromised immune systems is clinically significant and requires validation.