Non-epithelial endoscopic colon polyps: a focus on mesenchymal lesions

The majority of mesenchymal polyps in the gastrointestinal tract arise in the colorectum. Pathologists are often faced with the task of diagnosing these lesions, which can be difficult because many of the lesions share histologic features. This review is organized by layer of the colon as many of these mesenchymal lesions classically arise in a preferred layer of the colon and knowledge of the locations helps refine the differential diagnosis. In addition to a discussion on the preferred location of these lesions, the important clinical, histopathologic, and immunophenotypic features related to the most common colonic mesenchymal polyps are presented to aid the practicing pathologist in accurate diagnosis. Differentiating these mesenchymal lesions can have profound implications for the patient as many of these lesions are associated with clinical syndromes.