Extranodal Rosai-Dorfman Disease With Mucosal Involvement of the Stomach in a Background of Autoimmune Atrophic Gastritis.

Rosai-Dorfman disease (RDD), or sinus histiocytosis with massive lymphadenopathy, has been described involving both lymph nodes and extranodal sites, but extranodal RDD rarely involves the gastrointestinal tract. Although the etiology is unclear, several risk factors have been shown to be highly associated with this disease process, including viral infection and immune alterations. In this article, we present a case of a 79-year-old male with a history of autoimmune atrophic gastritis and multiple carcinoid tumors of the stomach presenting with a new stomach mass. An additional large sigmoid colon mass and adjacent enlarged lymph node was identified through imaging, prior to surgery. Through extensive pathologic analysis, we identified the first case of predominant extranodal RDD involving gastric mucosa and submucosa in a background of atrophic gastritis, with additional involvement of the sigmoid colon. Based on this case and literature review, we further discuss possible risk factors and pathogenesis of this disease process.