Shoulder Myeloid Sarcoma: An Initial Presentation of CML Blast Crisis

Myeloid sarcoma (MS) represents extra medullary accumulation of the immature cells of granulocytic series and occurs most commonly in the setting of acute myelogenous leukemia. Its occurrence in chronic myeloid leukemia (CML), myelodysplastic syndrome and other myeloproliferative neoplasm is uncommon. We here in report a 35-year old lady who was diagnosed as CML-chronic phase (CP) in the year 2004 and was on imatinib (400 mg OD) since then with regular follow up and good compliance. She had progression to accelerated phase in April 2014 which was managed by increasing the dose of imatinib to 600 mg OD. In August 2015, she presented with complaints of pain and swelling of the left shoulder suggestive of septic arthritis. Investigations revealed an ill-defined lesion involving muscles around the shoulder and clavicle. Absence of response to antibiotics and negative work up for infectious etiology raised the suspicion for MS which was later confirmed by immunohistochemistry of the aspirate from the lesion. Bone marrow examination was consistent with CML-CP. Hence, the diagnosis of CML with extra medullary blast crises was made. Patient was treated with a combination of high dose imatinib, hydroxyurea, cytarabine and local radiotherapy. Rarity of MS involving the shoulder and it's resemblance to septic arthritis has been highlighted in the present case. We emphasize the importance of immunohistochemistry of the aspirate for the timely and correct diagnosis of the cases who do not respond to an initial antibiotic trial.