7 yo native American previously healthy boy presented with high fever, hepatomegaly, skin rash. CBC showed pancytopenia (Hg 8g/dL, WBC 1.8K/ul, plt 21 K/ul). Labs: increased LDH, ferritin, triglyceride, liver enzyme, soluble CD25. PCR test was positive for EBV and influenza. Bone marrow was examined and show the following findings.