Incidental Langerhans cell histiocytosis of the parotid gland resembling marginal zone B-cell lymphoma: a case report.

Langerhans cell histiocytosis (LCH) manifesting as a parotid gland mass is an extremely rare clinical presentation. We report a case of LCH involving the bilateral parotid glands in an 81-year-old Japanese female. Pathologically, the lesion was characterized by numerous lymphoid follicles, dense lymphoplasmacytoid infiltrate and cystic dilatation of the parotid gland duct in addition to nodular and diffuse proliferation of LCs. Moreover, both LCs and small T-lymphocytes invaded the ductal epithelium forming a lymphoepithelial lesion-like morphology. The present case indicates that LCHs should be added to the different diagnosis for marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type involving the salivary glands.