14 December 2016 - Case of the Week #410

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Case of the Week #410

Clinical history:
A 68 year old man with a history of microscopic colitis had gastric thickening on CT scan, leading to esophagogastroduodenoscopy (EGD) with biopsy.


Micro images:




What is your diagnosis?































Diagnosis:
Russell body gastritis


Discussion:

Special stains:

CD138



Russell body gastritis (RBG) is a very rare, well circumscribed lesion of plasma cells containing Russell bodies in the mucosa of the stomach. Russell bodies are round, cytoplasmic, eosinophilic globules composed of immunoglobulins, not to be confused with Dutcher bodies, which are intranuclear inclusions in plasma cells (a plasma cell with Russell bodies is called a Mott cell). Russell bodies are thought to arise from excess immunoglobulins due to dysfunctional secretion (Arch Pathol Lab Med 2004;128:915). As seen in this case, extracellular Russell bodies can be present in the stroma (Hum Pathol 2010;41:134).

Patients with RBG generally present with epigastric pain and dyspepsia, which prompts endoscopic evaluation, typically showing a swelling or nodule, but possibly a fungating, ulcerated mass resembling malignancy (BMJ Case Rep 2014 Mar 26;2014, J Gastrointestin Liver Dis 2012;21:97).

Most reported cases are associated with H. pylori infection, and resolve after eradication treatment (BMJ Case Rep 2014 Mar 26;2014, ACG Case Rep J 2016;3:e96). However, upon further evaluation, some patients may have monoclonal gammopathy of undetermined significance (MGUS), which is also associated with H. pylori infection (Arch Pathol Lab Med 2004;128:915), and co-existence with myeloma has been reported (BMJ Case Rep 2014 Mar 26;2014). One reported case with both H. pylori and MGUS showed lamba light chain restriction. Therefore, the clinical significance of RBG - whether reactive / inflammatory or potentially neoplastic - is uncertain (World J Gastrointest Endosc 2015;7:73).

It is important to recognize RBG because it can simulate signet ring adenocarcinoma and MALT lymphoma. On low power, the Mott cells may resemble signet rings, but on high power, the cytoplasmic inclusions are eosinophilic, not clear, and the plasma cells in RBG lack nuclear atypia. Staining for PAS may be a pitfall, because Russell bodies stain positive similar to signet ring cells; however, mucin stains are negative in the Mott cells and positive in signet ring cells. In difficult cases, immunohistochemistry can help, as plasma cells are negative for keratins (Montgomery: Biopsy Interpretation of the Gastrointestinal Tract Mucosa: Volume 1: Non-Neoplastic, 2nd ed, 2011).

RBG can be distinguished from MALT lymphoma because it lacks lymphoepithelial lesions, atypia and Dutcher bodies; additionally, almost all RBG cases lack light chain restriction. However, plasma cells with Russell bodies can be seen both in MALT lymphoma and signet ring cell cancers, and have even been reported in a case with both MALT lymphoma and adenocarcinoma (Histopathology 2011;58:1178, Hum Pathol 2010;41:134), so malignancy should be carefully ruled out before rendering a diagnosis of RBG.


Discussion by: Dr. Hillary Z. Kimbrell, Myriad Genetics, Inc., Utah (USA), with special thanks to Dr. John Schmieg, Tulane University, Louisiana (USA)