Granulocytic sarcoma presenting as pneumonia in a child with t(8;21) acute myelogenous leukemia: diagnosis by fluorescent in situ hybridization.

Granulocytic sarcoma is a soft tissue collection of leukemic cells. The authors describe a 4-year-old boy with M2 acute myelogenous leukemia (AML) who presented with fever, mild nonproductive cough, and hematemesis. Although he was initially diagnosed with nodular pneumonia, rapid resolution of a pulmonary infiltrate following induction chemotherapy was suggestive of a pulmonary granulocytic sarcoma. Interphase fluorescent in situ hybridization (FISH) of the lung biopsy specimen for the t(8;21)(q22;q22) translocation confirmed the retrospective diagnosis of a well-differentiated pulmonary granulocytic sarcoma. Pulmonary granulocytic sarcomas may be underrecognized in children with AML; this may delay anti-leukemic therapy and may lead to ineffective therapy if misdiagnosed as pneumonia.