Gastrointestinal Langerhans cell histiocytosis with unifocal, single‐system involvement in adults: Cases report and literature review

BACKGROUND: Langerhans cell histiocytosis (LCH) is characterized by unifocal, multifocal single‐system, or multi‐system disease that occurs in all age groups, while it primarily attacks pediatric patients. Solitary gastrointestinal (GI) LCH in adults is exceedingly rare, so we aimed to investigate GI LCH in adults with unifocal single‐system involvement and clarified the clinicopathologic characteristics of this disease. METHODS: Two cases of solitary GI LCH in adults were presented, and the clinicopathologic features of this diagnosis in the literature were reviewed. RESULTS: The main diagnostic feature of LCH is the morphologic identification of the characteristic Langerhans cells with prominent nuclear grooves and abundant eosinophilic cytoplasm, accompanied by a variable number of lymphocytes, eosinophils, and plasma cells. The distinctive cells expressed S100, CD1a, and langerin (CD207) on immunohistochemistry. BRAF V600E mutations were detected in the two patients. CONCLUSIONS: Gastrointestinal Langerhans cell histiocytosis in adults with unifocal, single‐system involvement is extremely rare. Most patients were asymptomatic and usually a small solitary polyp in GI tract can be observed under routine endoscopy. Although the overall prognosis of unifocal single‐system LCH is favorable, long‐term follow‐up is still necessary to rule out systemic disease.