Extramedullary Blast Crisis of Chronic Myelogenous Leukemia With a Skin Lesion: A Case Report and Literature Review.

Extramedullary blast crisis of chronic myeloid leukemia (CML) is defined as extramedullary disease composed of blasts regardless of the proliferation of blasts in the bone marrow. The commonly affected sites are the lymph node, central nervous system, bone, skin, and soft tissue. However, skin infiltration of CML patients as the initial presentation while their bone marrow is still in the chronic phase is extremely rare. In this article, we present a case of a 51-year-old woman who was admitted to our hospital complaining about a skin nodule in her right calf and easy fatigability for 1 week. The peripheral blood and bone marrow analysis both supported the diagnosis of CML in the chronic phase, whereas the excisional biopsy specimen obtained from her right calf showed immature cells infiltration, and fluorescence in situ hybridization test was positive for p210 BCR/ABL1 gene rearrangement. Based on the presence of extramedullary myeloid sarcoma, the patient was diagnosed with extramedullary myeloid blast crisis of CML despite the chronic phase in the bone marrow.