Pediatric acute leukemia presenting as bilateral renal enlargement - Report of a case with fine needle aspiration cytologic features suggestive of megakaryocytic differentiation

BACKGROUND Fine needle aspiration (FNA) cytologic diagnosis of acute myeloi d leukemia involving the kidney has rarely been reported, but acute leukemi a with cytologic features suggestive of megakaryocytic differentiation has not been described before. CASE: An 8-month-old male presented with an abdominal swelling, bilateral c ervical and inguinal lymphadenopathy and enlarged left epididymis. Ultrason ography of the abdomen revealed a space-occupying lesion in the liver and b ilateral enlargement of the kidneys. FNA smears from the right kidney and r ight submandibular lymph node showed numerous blast cells. Since rare blast cells were positive for myeloperoxidase, a cytodiagnosis of involvement by acute myeloid leukemia (AML) was made. However, following the hematologic diagnosis of acute megakaryoblastic leukemia (M7) from peripheral blood and bone marrow smear examination, FNA smears were reviewed. There were cytopl asmic blebs or protrusions in the blast cells and cytologic features sugges tive of their differentiation toward micro-megakaryocytes and megakaryocyte s. There was also evidence of shedding of platelets, including numerous gia nt platelets. The reviewed FNA cytodiagnosis was suggestive of AML (M7). CONCLUSION: Extramedullary involvement by acute megakaryoblastic leukemia ( M7) can be suspected based on cytomorphologic features in FNA smears.