Cutaneous leukemia is characterized by red or purple slightly elevated papules or nodules; patients with cutaneous myelofibrosis may also develop red or purple slightly elevated papules or nodules. Cutaneous leukemia is a malignancy of the white blood cells in the blood and is characterized by diffuse infiltration of the bone marrow by immature leukocytes and abnormal numbers of immature leukocytes in the blood. In addition, immature leukocytes often infiltrate extensively the liver, spleen, lymph nodes and other organs, including the skin. Cutaneous myelofibrosis, also known as cutaneous extramedullary hematopoiesis, is a chronic myeloproliferative disease. So what is the cause of the red or purple, slightly elevated papules or nodules pathology? Here’s what you need to know. Myelofibrosis of the skin is a red or purple, slightly elevated papule or nodule with a patchy perivascular and periadnexal infiltrate or diffuse infiltrate located in a loose mucus-like stroma with a large number of vessels visible in the dermal reticular layer, infiltrate consisting of erythropoietic cells, myeloid cells and megakaryocytes, or erythropoietic cells and myeloid cells or myeloid cells only, with clusters of nucleated erythrocytes and dark and High magnification reveals clusters of nucleated erythrocytes with dark, spherical nuclei and bright red eosinophilic glassy cytoplasm, and Leder staining confirms myeloid cells at various stages of maturation.