BackgroundThe World Health Organization classification of myeloproliferative neoplasms discriminates between essential thrombocythemia and the prefibrotic phase of primary myelofibrosis. This discrimination is clinically relevant because essential thrombocythemia is associated with a favorable prognosis whereas patients with primary myelofibrosis have a higher risk of progression to myelofibrosis or blast crisis. Design and MethodsTo assess the reproducibility of the classification, six hematopathologists from five European countries re-classified 102 non-fibrotic bone marrow trephines, obtained because of sustained thrombocytosis. ResultsConsensus on histological classification defined as at least four identical diagnoses occurred for 63% of the samples. Inter-observer agreement showed low to moderate kappa values (0.28 to 0.57, average 0.41). The percentage of unclassifiable myeloproliferative neoplasms rose from 2% to 23% when minor criteria for primary myelofibrosis were taken into account. In contrast, the frequency of primary myelofibrosis dropped from 23% to 7%, indicating that the majority of patients with a histological diagnosis of primary myelofibrosis did not fulfill the complete criteria for this disease. Thus, over 50% of cases in this series either could not be reproducibly classified or fell into the category of unclassifiable myeloproliferative neoplasms. ConclusionsWorld Health Organization criteria for discrimination of essential thrombocythemia from prefibrotic primary myelofibrosis are poorly to only moderately reproducible and lead to a higher proportion of non-classifiable myeloproliferative neoplasms than histology alone.

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Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disorder characterized by pancytopenia, hemolysis, and thrombosis. Abdominal vein thrombosis is a life-threatening manifestation of this disease. We present a patient with complete spleen necrosis due to thrombosis of the splenic vessels. After splenectomy, other causes of thrombophilia were excluded and the diagnosis of PNH was established. The patient was put on anticoagulation but despite the prophylactic international normalized ratio maintained over the last 18 months of follow-up, he had another episode of intrahepatic thrombosis which was treated with tissue plasminogen activator thrombolysis.

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Histiocytic necrotizing lymphadenitis (HNL), or Kikuchi-Fujimoto disease, is a benign, self-limited disease that predominantly occurs in women. The etiology remains undetermined, although a viral or autoimmune hypothesis has been suggested. The disease usually emerges with cervical lymphadenopathy with or without fever. The diagnosis can be confirmed only by histological findings of lymph node biopsy, characterized by necrosis and histiocytic infiltration without neutrophils. We report a case of a 28-year-old woman with a medical history of two episodes of unexplained pulmonary embolisms (3 and 2 years previously) who was admitted to our hospital because of unilateral cervical lymphadenopathy and mild fever that presented 1 week before admission. A diagnosis of HNL was performed by lymph node biopsy. In parallel, whereas the laboratory tests for inherited thrombophilia were negative, a progressive elevated titer of anti-beta(2) glycoprotein I (GPI) antibodies was established. Because of persistent fever, the patient received a short course of corticosteroid therapy and she recovered completely from the HNL after 2 months. It is noteworthy that to date the patient has displayed an elevated titer of anti-beta(2) GPI antibodies (18 months after the recovery from the HNL). Thus, considering the previous history of venous thrombosis and the presence of antiphospholipid antibodies, the diagnosis of primary antiphospholipid syndrome associated with HNL was made. To our knowledge, this is the first report in the literature describing antiphospholipid syndrome associated with HNL. Moreover, a brief literature review is provided with emphasis on the etiology, clinical course, and pathogenesis of this rare disease entity.