Presentation of Childhood CML Mimicking Bone Sarcoma To the Editor: Chronic myeloid leukemia (CML) is a clonal disorder of pleuripotent hematopoietic stem cell characterized by a balanced, reciprocal translocation involving chromosomes 9 and 22 [1]. It has a triphasic course: chronic phase (CP), accelerated phase and blast crisis (BC). BC is the terminal phase of CML [2], characterized by 20% circulating or marrow blasts and/or extramedullary blastic lesions [3]. This phase is associated with treatment refractoriness and median survival of 3 –9 months. CP is usually the initial presentation of CML, BC may be the presenting manifestation in 10% of cases but extramedullary BC at presentation is rare [3]. We report a child who presented with a bone fracture and swelling mimicking a sarcoma and was found to be CML in extramedullary BC. A 16-year-old male presented with a painful upper left arm 8 cm  4 cm swelling of 1-month duration. An outside fine needle aspiration cytology from the swelling was suggestive of Ewing sarcoma. Radiograph of arm showed a soft tissue mass infiltrating upper metaphyseal region of left humerus, resulting in fracture (Fig. 1A). Additional physical examination revealed 11 cm splenomegaly. Hemogram showed hemoglobin 9.2 g/dl; white blood cell count was 32,500/mm 3 and platelets were 1,128,000/mm 3 . Peripheral smear, bone marrow aspiration and biopsy (Fig. 1B) was consistent with CML BC. Bone biopsy from humerus showed extra- medullary BC co-expressing myeloid (myeloperoxidase, CD 33) and lymphoid immunophenotypes (CD3, cytoplasmic CD3) (Fig. 1C). Further, bone marrow biopsy showed myeloid predom- inance, micromegakaryocytes and grade III reticulin fibrosis. Peripheral blood RT-PCR was positive for the bcr/abl translocation. Thus a diagnosis of CML-BC with extramedullary involvement of upper left humerus was made. He was initially treated with imatinib, 400 mg once daily, to which he had a partial response lasting for 2 weeks. Subsequently, vincritine, prednisolone and daunorubicin were added to imatinib. He again had a partial response lasting 3 weeks and then died of progressive disease. Approximately 65% of CML patients evolve to myeloid BC, 30% have B-lymphoid blasts and 5% have undifferentiated or T-cell blasts [4]. Occasionally, isolated BC of extramedullary origin may occur while the patient’s marrow otherwise meets criteria for CP. In previous reports, it has been found that extramedullary BC usually precedes hematological blast crisis and that 80% of CML patients died within 6 months after extramedullary BC [1]. In extramedullary BC, lymphoid BC is more responsive to treatment and has longer survival than myeloid extramedullary BC [5]. Similar to medullary BC, imatinib has been found to be useful in management of extramedullary BC [6]. In an analysis of 15 cases of extramedullary CML BC, common sites were the lymph nodes (13/15), central nervous system (1/15), and orbital region (1/15) [5]. The presence of disease in such sites is usually associated with significantly poorer response to therapy and survival. There has been 1 previous report wherein bone (with pathological fracture) was the site of BC [7]. Thus, our case is presented for its rare presenting feature and importance of peripheral smear examination. Sourabh Radhakrishnan, MD Department of Medical Oncology Dr. B.R.A. Institute Rotary Cancer Hospital All India Institute of Medical Sciences New Delhi, India Prasenjit Das, MD Department of Pathology All India Institute of Medical Sciences New Delhi, India Sarika Singh, MD Dipti Kalita, DNB Department of Laboratory Oncology Dr. B.R.A. Institute Rotary Cancer Hospital —————— *Correspondence to: Dr. Sameer Bakhshi, Associate Professor of Pediatric Oncology, Department of Medical Oncology, Dr. B.R.A Institute Rotary Cancer Hospital, All India Institute of Medical sciences, New Delhi 110029, India. E-mail: sambakh@hotmail.com Received 30 November 2008; Accepted 13 January 2009 Fig. 1. Radiograph of the left shoulder shows a homogeneous predominantly soft tissue mass infiltrating the upper metaphyseal region of left humerus, causing fracture (A). Peripheral smear shows myeloblasts and myeloid precursors; myeloblasts have high nuclear cytoplasmic ratio and opened up chromatin (B). Photomicrograph from humerus biopsy shows sheets of cells showing irregularly clumped nuclear chromatin and scant to abundant amount of granular eosinophilic cytoplasm; few mitotic figures are also noted. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] ß 2009 Wiley-Liss, Inc. DOI 10.1002/pbc.21969 Published online 12 February 2009 in Wiley InterScience (www.interscience.wiley.com) Letters to the Editor 901