P1257 - Case Report of Colonic Schwann Cell Hamartoma: A Rare Benign Colonic Polyp

Nikisha Pandya, MD¹, Mohammad Choudhry, MD², Christopher Chum, DO², Vera Platsky, ^2
1New York City Health and Hospitals/Coney Island Hospital, Brooklyn, NY; ²Coney Island Hospital, Brooklyn, NY

Introduction: Colonic polyps that are neural in origin include Schwannomas, Neurofibromas, perineuromas and ganglioneuromas. Mucosal Schwann Cell Hamartomas (MSCH) are a rare disease of the colonic mucosa often diagnosed during screening colonoscopy. To our knowledge, only 12 case reports have been published. It is a relatively new entity first described in 2009 with need for more literature about its long-term prognostication. Accurate diagnosis and differentiation from other neuronal polyps are important as some are associated with familial syndromes with worse outcomes and different management than MSCH.

Case Description/Methods: A 64-year-old male with history of hypertension and Gastroesophageal Reflux Disease was referred for screening colonoscopy. He denied any weight loss, blood in stool, change in stool caliber or change in appetite. He also denied any family history of colon cancer or genetic disorders. Screening colonoscopy showed small sigmoid diverticula and three semi-sessile sigmoid polyps ranging 2 to 3 mm in size, which were removed with cold biopsy forceps. Pathology revealed one hyperplastic polyp and remaining polyps with globular structures containing neuropile-like fibers in the superficial lamina propria and a well-maintained mucosa. Immunostaining was positive for S-100 and negative for CD68 supporting the diagnosis of MSCH. PAS and AFB staining were negative ruling out fungal and tuberculous lesion, respectively.

Discussion: MSCHs are mesenchymal polyps most commonly found in the rectosigmoid colon during screening colonoscopy. Clinicians often have to rely on immunohistopathology for accurate diagnosis. Of all the mesenchymal polyps, it is crucial to differentiate benign MSCH from neurofibromas and ganglioneuromas. The latter are associated with clinical syndromes such as Neurofibromatosis 1 (NF1) and NF1, Cowden syndrome and multiple endocrine neoplasia IIB (MENIIB) respectively. A table differentiating different types of mesenchymal polyps is included for reference but most notable feature differentiating MSCH from other mesenchymal polyps includes cells uniformly staining for S100 protein and absence of axons or ganglion cells. MSCH is a benign entity with no need for surveillance colonoscopies but long-term implication of this relatively new disease entity remains unknown.


Figure: Figure 1: Biopsy Showing Multiple Bland Globular Structures With Neuropile-like Fibers In The Superficial Lamina Propria And a Well-maintained Mucosa (H&E x100)
Figure 2: Biopsy Showing Bland Globular Structure With Neuropile-like Fibers In The Superficial Lamina Propria (H&E x400)
Figure 3: Immunohistochemistry Stain Positive for S-100
Figure 4: Immunohistochemistry Stain Negative for CD68

Lesion	Characteristic cells	Immunohistology staining	Associations
Benign fibroblastic polyps/perineuroma	Spindle cells with abundant eosinophilic cytoplasm, limited to lamina propria	EMA*, claudin-1, GLUT-1*	None – benign
Mucosal Schwann Cell Hamartoma	Schwann cells, limited to lamina propria	S-100	None – benign
Mucosal Neuroma	Coiled, twisted nerves coated with perineurium	EMA*	MEN IIB
Kaposi Sarcoma	Spindle cells arranged in fascicles, separated by vessels	CD31, CD34, HHV-8*	Angiosarcoma, HHV-8*, HIV*
Ganglioneuroma	Spindle cells admixed with ganglion cells within mucosa and submucosa	S100, NSE*, NFP*, synaptophysin	MEN IIB, NF1, FAP*, Cowden syndrome, TB* and juvenile polyposis