Criteria: all of the following:
(1) splenomegaly
(2) leukoerythroblastic peripheral blood smear (presence of nucleated red blood cells and immature myeloid cells)
(3) tear-drop poikilocytosis
(4) increased reticulin in bone marrow biopsy
(5) absence of other chronic myeloproliferative disorders (polycythemia rubra vera, primary thrombocythemia, chronic myeloid leukemia)
(6) absence of other malignant disease (hairy cell leukemia, acute leukemia, metastatic carcinoma, lymphoma, etc.)
(7) absence of other explanation (radiation, toxic, autoimmune disease, granulomatous infection, endocrinopathy, etc.)
where:
• Extramedullary hematopoiesis occurs in the liver and spleen.
• Collagen may also be increased in the bone marrow biopsy.
• The increased marrow fibrosis is associated with difficulty in obtaining a bone marrow aspiration ("dry" tap).
