A Rare Case of Rosai-Dorfman Disease Involving Great Vessels of the Heart Mimicking Breast Cancer Recurrence.

Rosai-Dorfman disease (RDD) is a rare non-Langerhans histiocytosis, with cardiovascular involvement in <0.1% of cases. We report the case of a 69-year-old woman with history of breast cancer found to have mediastinal nodules involving the superior vena cava and pulmonary veins. Imaging suggested recurrence of malignant disease, and multiple biopsies were nondiagnostic. Definitive diagnosis was achieved after median sternotomy under cardiopulmonary bypass with superior vena cava resection and prosthetic reconstruction. Histopathologic analysis confirmed RDD with abundant IgG4-positive plasma cells. This case illustrates the diagnostic complexity of extranodal RDD and the role of surgery in cardiovascular involvement.