Sinus histiocytosis with massive lymphadenopathy, also known as Rosai-Dorfman disease, is a rare entity predominantly affecting children and young adults, characterized in 95% of patients by painless bilateral cervical limphadenopathy. We report the case of a 30-year-old female with an anterior mediastinal mass due to lymph node enlargement, which showed calcifications on computed tomography. To our knowledge, calcification in lymphadenopathy, as is present in this case, has never been described in Rosai-Dorfman disease.