Mesenchymal Tumors of the Tubular Gastrointestinal Tract (Non-GIST): The GI Pathologist's Approach.

Mesenchymal neoplasms of the gastrointestinal tract are rare compared with epithelial lesions. However, over the past few decades, the increasing volume of gastrointestinal endoscopy has expedited the recognition of several novel entities with varying clinical significance. Its spectrum extends from reactive changes and benign neoplasms to highly aggressive sarcomas.

Gastric-like (pseudopyloric and pseudofoveolar) metaplasia and Paneth cell hyperplasia-neglected histological features of chronic ileal inflammation.

Architectural distortion and basal plasmacytosis are the most widely recognized histologic features of chronic ileal inflammation. However, these features might be difficult to assess in small, poorly oriented, or superficial biopsies. Additional features of chronic mucosal damage, including pseudopyloric or pseudofoveolar metaplasia and Paneth cell hyperplasia, have been less commonly reported, and their broader appreciation could facilitate the diagnosis of chronic ileal inflammatory conditions.