Track: Case Reports

Topic: Lymphoproliferative Disorders

Abstract:

Extramedullary hematopoiesis (EMH) refers to the production of blood cells outside of the bone marrow and is often seen in fetal development or myeloproliferative disorders. EMH typically appears in the spleen, liver, lymph nodes, or occasionally in the skin. While commonly reported in primary myelofibrosis, cutaneous extramedullary hematopoiesis (CEH) is rare in chronic myeloid leukemia (CML). We present a case of CEH associated with CML treated at our institution. A 34-year-old male with CML presented with painful pustules. A skin punch biopsy on the right thigh showed a dermal infiltrate comprised of left-shifted maturing granulocytes, scattered megakaryocytes, rare erythroid precursors, and scattered plasma cells and lymphocytes. Immunohistochemical studies showed less than 5% blasts. The overall features were consistent with maturing EMH, without clusters of blasts suggestive of leukemia cutis. Peripheral blood review showed marked neutrophilic leukocytosis with basophilia and eosinophilia, and a bone marrow aspirate and biopsy showed marked hypercellularity with left-shifted granulocytic hyperplasia, megakaryocytic hyperplasia, erythroid hypoplasia, and less than 5% blasts. Further tests revealed BCR::ABL1 fusion, consistent with CML. CEH during chronic phase of CML is a feature that is not well-documented in the literature. This entity shows immature granulocytic precursors but does not exhibit an increase in blasts and therefore should not be called leukemia cutis or myeloid sarcoma. It is important to raise awareness of this entity to prevent misinterpretation as myeloid sarcoma and subsequent unnecessarily aggressive therapy.

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Jacob Armstrong, MD