[750] Hamartoma-Like Schwann Cell Proliferation and Architectural Distortion of the Appendix: A Study of 46 Appendiceal Diverticular Disease and Serrated Epithelial Lesions

Thomas Stockl, Otto Walter, Karen Dresser, Hwajeong Lee. Univ. of Massachusetts, Worcester, MA

Background: S-100 positive Schwann cell proliferation in the appendiceal mucosa has been known as intramucosal neuroma. The recently described entity “mucosal Schwann cell hamartoma" (MSCH) is a benign mucosal Schwann cell proliferation in colonic polyps and holds morphologic resemblance to intramucosal neuroma of the appendix. We identified benign spindle cell proliferations of the appendiceal lamina propria encountered in conditions of mucosal expansion including diverticular disease and serrated polyps, and studied the prevalence and distribution of MSCH-like lesions of the appendix.
Design: 46 appendectomy cases of diverticular disease (23) and serrated lesions (23) to include sessile serrated polyp, hyperplastic polyp, and epithelial hyperplastic change were retrieved from the surgical pathology files from 2000 to 2011. H&E slides were reviewed and distribution of the spindle cells in the lamina propria in relation to epithelial alteration or crypt architectural distortion, if present, was studied. Representative tissue sections from paraffin-embedded blocks were subject to immunoperoxidase staining for S-100, EMA and Neurofilament protein (NFP).
Results: 13 of 46 cases (28%) showed localized or diffuse proliferation of S-100 positive Schwann cells in the lamina propria associated with prominent crypt distortions. The mean age of the patients was 46 (22-77) years and included 7 females and 6 males. No patient had a history of a syndromic disorder. 10 mucosal schwann cell proliferations were from appendiceal diverticular cases. In 2 cases the secondary epithelial alterations had been interpreted as serrated adenoma (1) and epithelial hyperplastic change (1). One had been diagnosed as neural hyperplasia (1). No diffuse Schwann cell proliferation was seen within the serrated polyps. One case showed focal NFP staining mixed with Schwann cell proliferation. EMA was negative in the spindle cells of interest.
Conclusions: In the appendix with diverticular disease, MSCH-like prominent mucosal Schwann cell proliferation is common, being encountered in 43% (10 of 23) of the cases studied. The Schwann cell proliferation is usually associated with crypt architectural distortion. Awareness of this common finding of MSCH-like proliferation in the appendix is required to avoid misinterpreting secondary epithelial alterations as preneoplastic conditions. On the contrary, Schwann cells are inconspicuous within true serrated polyps of the appendix. Perineuriomas are uncommon in the appendix.
Category: Gastrointestinal

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 108, Monday Morning


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