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Intrathoracic Rosai Dorfman Disease with Focal Aggregates of IgG4-bearing Plasma Cells. Case Report and Literature Review.

Rosai Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy, is a rare histiocytic disorder that typically presents as painless cervical adenopathy. Occasionally, Rosai Dorfman disease may involve extranodal sites and it can be associated with constitutional symptoms. In this report, we present a patient with progressive dyspnea on exertion, obstruction on spirometry, and paratracheal soft tissue thickening extending to the proximal bronchi and hila. After extensive radiologic and interventional measures, including multiple biopsies, the diagnosis was established on pathology showing characteristic features of Rosai Dorfman disease in a paratracheal lymph node and features of extranodal Rosai Dorfman disease with extensive fibrosis in the paratracheal mass. In addition, the involved paratracheal lymph node demonstrated focally increased IgG4-positive plasma cells, a finding that was not present in the tracheal mass. A review of intrathoracic manifestations of Rosai Dorfman disease including the proposed causes and causative triggers is presented. The histological features and the current understanding of the management and prognosis are also discussed. This unusual presentation highlights the need to consider histiocytic disorders in the differential diagnosis of paratracheal disease.