PATHOLOGY

A 4-year-old girl died due to a post-hemorrhagic anemia, resulted from a gastro-intestinal profuse bleeding. An autopsy revealed an anemia of her organs, the enlargement of the different groups of lymph nodes, thymomegaly, mild hepatomegaly, splenomegaly and bright red bone marrow. Microscopical study showed hyper cellularity of a bone marrow with monomorphic blast cells infiltrate, diffuse inflammatory tumor-like infiltrates in a liver, a spleen, lymph nodes, meninges and substance of a brain. What is the most likely diagnosis?