Gastric amyloidosis: clinicopathological correlations in 79 cases from a single institution.

Gastrointestinal involvement by amyloidosis is common, but large clinicopathological studies specifically addressing gastric amyloidosis are lacking. Seventy-nine patients with biopsy-proven, gastric amyloidosis were identified by a retrospective review of our pathology archives, from 2007 to 2013. Amyloid typing was performed by laser microdissection/mass spectrometry (in 44 patients), immunohistochemistry, immunofluorescence, and/or genetic testing. The median age at diagnosis was 62years, with 61% being males. The amyloid was derived from immunoglobulin light chain (67%), transthyretin (ATTR) (18%), serum amyloid A (9%), and apolipoprotein A1 (3%). When other gastrointestinal sites were biopsied, amyloid was demonstrated in the small bowel (89%), colon (81%), and esophagus (33%). The most common gastrointestinal manifestations were weight loss (37%), abdominal pain/dyspepsia (23%), and nausea/vomiting (23%). Endoscopic findings included normal (35%), erythema (33%), erosions (18%), and nodularity (15%) and were not related to amyloid type. No case showed gastric lymphoma. The most common location of amyloid was the muscularis mucosae regardless of the type of amyloid. Lamina propria involvement was less frequent in ATTR than other types. In 22% of patients, the first diagnosis of amyloid was based on the gastric biopsy. Patients' survival at 3years was 60% and was not different by type of amyloid. Our study shows that light-chain amyloidosis is the most common form of gastric amyloidosis, followed by ATTR. Type of amyloid cannot be predicted based on clinical or endoscopic findings, and therefore, biopsy with amyloid typing, preferably by laser microdissection/mass spectrometry, is critical to establish the correct diagnosis, prognosis, and appropriate treatment.