Myeloid sarcoma as the presenting symptom of chronic myelogenous leukemia blast crisis.

Myeloid sarcoma is an extramedullary tumor composed of immature myeloid cells that efface the underlying tissue architecture. It is usually associated with acute myelogenous leukemia, but can be associated with myeloproliferative neoplasms, myelodysplastic disorders, or myeloproliferative/ myelodysplastic syndromes. If it is unrecognized, appropriate chemotherapy may be delayed and survival jeopardized.