Primary Rosai-Dorfman disease of lung and mediastinum: A clinicopathological and immunohistochemical study of five cases

Abstract

Objective: To explore the clinicopathological and immunohistochemical features of primary Rosai-Dorfman disease (RDD) in the lung and mediastinum.

Methods: Histological observation and immunohistochemical staining of 5 cases of pulmonary and mediastinal RDD, with a review of the related literature.

Results: Two cases were located in the trachea with involvement of the lung. One case was located in the left lower lung. Two cases were located in the mediastinum. Macroscopically, 1 case had clear boundaries, while 4 cases had unclear boundaries, and grayish-white on cut surfaces. Microscopically, low power view showing alternating light and dark areas. The dark areas comprise an admixture of lymphocytes and plasma cells. The light areas comprise the characteristic pale pink histiocytic cells. Histiocytes are large with round-to-oval nuclei, dispersed chromatin, prominent nucleoli, and abundant clear-to-foamy or vacuolated cytoplasm. Emperipolesis was observed in all five cases. All five cases showed interstitial fibrosis or sclerosis and Russell bodies. Four cases (4/5, 80 %) showed lymphoid follicles with germinal centers in the interstitium. Four cases showed (4/5, 80 %) interstitial neutrophil infiltration, with three cases accompanied by microabscess formation. Immunophenotypically, the histiocytes expressed Cyclin D1(5/5, 100 %), OCT2 (5/5, 100 %), S100 protein (5/5, 100 %), CD68 (5/5, 100 %), CD163 (5/5, 100 %), BCL2 (5/5, 100 %) and CD30 (3/5, 60 %), but did not express CD1a, Langerin, IgG4 and ALK.

Conclusion: RDD of the lung and mediastinum is rare, with a wide range of ages. Histologically, there are often lymphoid follicles with germinal centers and interstitial fibrosis or sclerosis. This together with the expression of BCL2 and CD30 in the histiocytes can lead to misdiagnosis of lymphomas or other lymphoproliferative diseases or missed diagnosis, particularly in the mediastinum. Careful histological examination for the diagnostic feature of emperipolesis together with characteristic Cyclin D1, OCT2, S100 protein, and CD68 positivity are important clues for accurate diagnosis.

Keywords: Cyclin D1; Emperipolesis; OCT2; Rosai–Dorfman disease; S-100; Thoracic.