Colonic Mucosal Schwann Cell Hamartoma With Ancient Change: A Deceptive Feature for a Rare Lesion

Mucosal Schwann cell hamartomas are relatively rare, incidental, benign neural tumors of the colonic mucosa. They are characterized by an ill-defined proliferation of spindle cells in the lamina propria, are thought to originate from Schwann cells, and hence are diffusely positive for S100 immunostain. Mucosal Schwann cell hamartomas differ from neurofibromas and ganglioneuromas due to the absence of syndromic associations. Differentiating mucosal Schwann cell hamartomas from other mesenchymal lesions of the colon is clinically important due to their benign course and lack of syndromic associations. Schwannoma, another neural tumor, commonly shows ancient changes, which are defined by large, irregular hyperchromatic nuclei without atypical mitosis or necrosis. Here, we report a rare lesion of colonic mucosal Schwann cell hamartoma with ancient changes (as described in schwannomas) to increase awareness of histologic variations associated with mucosal Schwann cell hamartomas.