Background: Granulocytic sarcoma is a rare tumor that is often misdiagnosed as it can be confused with lymphoma. It has unique cytologic features independent of the site of the tumor and can be identified on fine needle aspiration.
Case: A 13-year old girl without a relevant medical history presented with an abdominal mass. Investigation revealed a tumor infiltrate in the small intestine and mesentery. The fine needle aspirate contained myeloid blasts with cytoplasmic granules. Immunohistochemistry on subsequent biopsy confirmed myeloid differentiation. There was no evidence of blood or bone marrow involvement suggestive of acute leukemia. The patient was well after 27 months of follow-up.
Conclusion: Granulocytic sarcoma should be included in the differential diagnosis of any small intestine infiltrate. Cytomorphology is accurate and efficient for the diagnosis in conjunction with complete immunocytochemistry study.