J Korean Med Sci 2006; 21: 936-9 ISSN 1011-8934 Copyright The Korean Academy of Medical Sciences A Case of Leukemic Pleural Infiltration in Atypical Chronic Myeloid Leukemia Pleural effusion in chronic myeloid leukemia (CML) is poorly understood and rarely reported in the literature. When the pleural effusion is caused by leukemic pleural infiltration, the differential white blood cell count of the effusion is identical to that of the peripheral blood, and the fluid cytology reveals leukemic blasts. We report here a case of bilateral pleural involvement of atypical CML in an 83-yr old male diagnosed with pancreatic cancer with abdominal wall metastasis and incidental peripheral leukocytosis. Based on bone marrow examination, chromosome analysis and poly- merase chain reaction he was diagnosed with Philadelphia chromosome negative, BCR/ABL gene rearrangement negative CML. Following 3 months of treatment with gemcitabine for pancreatic cancer, he developed bilateral pleural effusions. All stages of granulocytes and a few blasts were present in both the pleural fluid and a peri- pheral blood smear. After treatment with hydroxyurea and pleurodesis, the pleural effusion resolved. Key Words : Pleural Effusion; Atypical Chronic Myeloid Leukemia; Leukemia, Myeloid, Chronic Hyun Woo Kim, Sung Sook Lee, Min-Hee Ryu, Jae Lyun Lee, Heung Moon Chang, Tae Won Kim, Hyun-Sook Chi*, Woo Kun Kim, Jung Shin Lee, Yoon-Koo Kang Departments of Internal Medicine, Laboratory Medicine*, University of Ulsan College of Medicine, Seoul, Korea Received : 27 June 2005 Accepted : 17 August 2005 Address for correspondence Yoon-Koo Kang, M.D. Department of Internal Medicine, University of Ulsan College of Medicine, 388-1 Poongnap-dong, Songpa-gu, Seoul 138-736, Korea Tel : +82.2-3010-3210, Fax : +82.2-3010-6961 E-mail : ykkang@amc.seoul.kr INTRODUCTION Atypical chronic myeloid leukemia (CML) is negative for both the Philadelphia chromosome and BCR/ABL gene rear- rangement (1). During the course of CML, 37% of patients develop extramedullary disease in sites such as the lymph nodes, spleen, or meninges (2), but, pleural effusion due to leukemic infiltration in this disease is rare. In this paper, we describe a patient who developed pleural effusion during treat- ment for atypical CML and pancreatic cancer. The pleural effusions were cleared after treatment with hydroxyurea and pleurodesis. CASE REPORT An 83-yr-old male patient with leukocytosis was admitted to our hospital on September, 2004. His medical history in- cluded an early gastric cancer and distal gastrectomy in 1989, and a right lobectomy for non small cell lung cancer in May 2004. One month prior to the admission, he was diagnosed as having pancreatic tail cancer with abdominal wall metas- tasis, which had not been treated surgically or with chemo- therapy. On physical examination, the patient’s liver and spleen were not palpable. A tender and firm mass, measuring 1×2 cm, 936 was noted on the periumbilical abdominal wall. Hematologic findings were Hb 10.6 g/dL, WBC 71×109/L (neutrophil 58%, lymphocyte 7%, monocyte 13%, eosinophil 3%, pro- myelocyte 2%, myelocyte 10%, metamyelocyte 4%, blast 1%, normoblast 1/100 WBC), and platelet 192×109/L. Patho- logic examination showed that his palpable abdominal wall mass was a metastatic adenocarcinoma that differed from the previous non small cell lung cancer. Immunohistochemically, the tumor cells were positive for cytokeratin 7 (CK7) and negative for thyroid transcription factor 1 (TTF-1) and cyto- keratin 20 (CK20), whereas his non small cell lung cancer cells had been positive for TTF-1 and CK7 and negative for CK20. Bone marrow examination showed hypercellular marrow (cel- lularity 90%) containing cells at all stages of granulocytic hyperplasia and 0.6% blasts. There were some hypogranular myelocytes, indicating dysgranulopoiesis (Fig. 1). Polymerase chain reaction for BCR/ABL fusion gene was negative. The leukocyte alkaline phosphatase (LAP) activity score was 13 (reference range 30-130). Computed tomography of the ab- domen showed a solid mass in the tail of the pancreas with attachment to the spleen and invasion of the spleen and splenic artery by the mass, leading to splenic infarction (Fig. 2). Based on these results, he was diagnosed with atypical CML. He was treated with gefitinib 250 mg/day for metastatic pancre- atic cancer and hydroxyurea 1,500 mg/day plus allopurinol for atypical CML. Treatment with hydroxyurea was interrupt-