Leukemic ascites as an initial presentation of acute myelomonocytic leukemia with inversion of chromosome 16.

To the Editor: The inversion of chromosome 16, inv(16), a cytogenetic abnormality expressed in core binding factor acute myeloid leukemias (AML), is associated with myelomonocytic differentiation and eosinophilia.1 Even though inv(16) generally portends a good prognosis, accompanying mutations detected by molecular genetic methods, such as KIT and Ras mutations, alter their response to treatment. 2 Infiltration of leukemic cells into serous effusions is unusual. To our knowledge, there are only a few reports of AML with inv(16) presenting with leukemic ascites.2

We present a 33-year-old woman with jaundice and massive ascites. The laboratory tests showed the following: hemoglobin 8.3 g/dL, hematocrit 25%, total leukocyte count 135 800/mm3, and platelet count 32 000/mm3, erythrocyte sedimentation rate 45 mm/hr, AST 597 U/L, ALT 111 U/L, ALP 417 U/L, GGT 191 U/L, lactate dehydrogenase 6515 U/L, total bilirubin 9 mg/dL and direct bilirubin 8.2 mg/dL. On peripheral blood smear, myeloblasts comprised 67% of the cells and the bone marrow analysis showed 57% myeloblasts with eosinophilic differentiation. Immunophenotypic analysis of the bone marrow was positive for CD13, CD14, CD45, CD33, CD34 and HLA-DR. FISH analysis of the bone marrow revealed an inv(16) signal. The final diagnosis was acute myelomonocytic leukemia (FAB Classification M4e) with inv(16). Abdominal computed tomography revealed massive ascites and multiple lympadenopathies with a maximal diameter of 1.5 cm at the mesenteric region. A diagnostic and therapeutic paracentesis was performed. Analysis of the ascitic fluid showed an exudate with a white blood cell count 3140 cells/ mL; red blood cell count 70000 cells/mL; monocyte count 1910 cells/mL. The ascitic total protein was 3.9 g/dL (serum, 7.1 g/dL), glucose 208 mg/dL (serum, 216 mg/ dL), lactate dehydrogenase 1918 U/L (serum, 2813 U/L) and albumin 2.4 g/dL (serum, 3.9 g/dL). Cytocentrifuge preparation of the patient’s ascitic fluid showed myeloblasts and monoblasts with irregular nuclei and prominent nucleoli (Figure 1). Flow cytometric analysis of the ascitic fluid showed the expression of CD13, CD14, CD33, CD34, CD45 and HLA-DR compatible with the diagnosis of acute myeloid leukemia-M4 (AML-M4) (Figure 2). The patient was treated with cytarabine 100 mg/m2 for 7 days and idarubucin 12mg/m2 for 3 days. On the third day of the remission induction therapy, ascites disappeared and the liver enzymes and bilirubin levels returned to normal on completion of the first week of therapy. The patient was under follow up at our hematology department at the time of writing.

Figure 1

Ascitic fluid with monoblasts and myeloblasts.

Figure 2

Flow cytometric analysis of the ascitic fluid showed the expression of CD13, CD14, CD33, CD34, CD45 and HLA-DR.

Leukemic infiltration of effusions have been mostly reported in AML with monocytic differentiation, including M4 and M5 AML in the FAB classification.3,4 Yet, development of leukemic ascites at initial presentation of AML, as in our case, is a rare entity.5 Also, in few previous cases, leukemic ascites has been reported as the presenting feature in inv(16) AML.2 Our case emphasizes the importance of performing paracentesis and an extensive diagnostic work-up in AML presenting with ascites to differentiate leukemic infiltration from other causes. Further studies are needed to to identify the clinical significance of inv(16) in the presence of leukemic ascites.