Case ReportsMalignant Histiocytoses/Disseminated Histiocytic Sarcoma With Hemophagocytic Syndrome in a Patient With Mediastinal Germ Cell TumorShinoda, Hiroko MD; Yoshida, Akihiko MD; Teruya-Feldstein, Julie MDAuthor Information Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York Reprints: Julie Teruya-Feldstein, MD, Immunohistochemistry Laboratory and Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Rm C502, Box 36, New York, NY 10021 (e-mail: firstname.lastname@example.org). Received for publication May 9, 2008; accepted August 7, 2008 Images for Figures 1 to 3 were obtained with the Olympus DP20 Camera from Center Valley, PA. Image acquisition and processing software was performed using Adobe Photoshop 7.0 and DP20 software. Applied Immunohistochemistry & Molecular Morphology: July 2009 - Volume 17 - Issue 4 - p 338-344 doi: 10.1097/PAI.0b013e3181897e8e Buy Metrics Abstract We describe a case of a 24-year-old man with a large anterior mediastinal mass showing a nonseminomatous germ cell tumor then subsequently developed hemophagocytic syndrome involving the bone marrow and liver. During the course of chemotherapy, he developed profound thrombocytopenia, eccymoses, and bleeding. He had moderate splenomegaly and splenectomy was performed to restore adequate hematologic reserve to permit further chemotherapy. The spleen showed marked erythrophagocytosis and markedly atypical histiocytes consistent with malignant histiocytoses. Atypical histiocytes stained positive for CD68, CD163, CD4, CD45 (LCA), and S-100. Cytogenetics studies were negative for i12p. The patient was refractory to therapy and ultimately died 5 months after diagnosis. © 2009 Lippincott Williams & Wilkins, Inc.