The atypical histiocytes were positive for CD68 and lysozyme and negative for lymphoid markers, and the diagnosis of true malignant histiocytosis associated with mediastinal germ cell tumor was made.
We stress the importance of the CD68 marker in the diagnosis of true histiocytic lymphoma, suggest a therapeutic approach based on similarities with monocytic leukemia, and propose the use of the term monocytic sarcoma for this clinicopathological presentation.