Abstract 4472 Background Because there is no single clinical or laboratory finding for the diagnosis of essential thrombocythemia (ET), a differential diagnosis of other myeloproliferative neoplasms or reactive thrombocytosis (RT) is always necessary. Developments in automated blood cell analysers can now measure various platelet indices and were used in this study to differentiate between ET and RT in patients with a platelet count of 600×103/μL or more. Method The subjects studied were 31 patients with ET and 224 patients with RT. The platelet counts, mean platelet volume (MPV), plateletcrit (PCT), platelet distribution width (PDW), mean platelet mass (MPM), mean platelet component concentration (MPC) and large platelets (LPLT) were measured by ADVIA 120 (Bayer Diagnostics, USA) and the sensitivity and specificity of the two groups were determined. Results In essential thrombocythemia, all parameters except MPC were higher than those of reactive thrombocytosis and were statistically significant. The sensitivity and specificity were 74.2% and 84.4% when the platelet count was more than 820×103/μL. The sensitivity and specificity were 80.6% and 80.0% when the plateletcrit was more than 0.63%. The sensitivity and specificity were 64.5% and 99.1%, respectively, when LPLT was more than 23×103/μL. Conclusion The platelet counts and platelet indices are important for the differential diagnosis of thrombocytosis. The comparison of the plateletcrit and LPLT is particularly useful when the platelet count is markedly increased. Disclosures: No relevant conflicts of interest to declare.

Biphenotypic acute leukemia (BAL) is a rare type of leukemia, comprises 4% of all acute leukemias. It is more common in adults and the clinical features, as related to marrow dysfunction, are similar to those found in other patients with acute leukemia. BAL commonly shows a dimorphic blast population with, one resembling lymphoblasts and the other resembling myeloblasts. The majority of BAL patients express B-lymphoid and myeloid markers. BAL can be diagnosed by morphologic studies and by a comprehensive panel of immunological markers, as well as cytogenetic/molecular studies, such as fluorescence in situ hybridization (FISH) and reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, its prognosis is relatively poor. We present here a 27 year-old female patient who showed lymphoblasts and myeloblasts on her marrow studies and these cells were positive for myeloid and B-lymphoid markers on the immunophenotypic studies. Chromosome analysis revealed 46, XX, t(6;19)(p23;p13.1), t(9;22)(q34;q11.2). A major (b3a2) type of BCR-ABL1 mRNA transcript was detected by RT-PCR, and a 5'ABL1 deletion was identified by FISH.

BACKGROUND For the diagnosis of essential thrombocythemia (ET), no single clinical or laboratory finding of diagnostic value is available and a differential diagnosis of other myeloproliferative neoplasms or reactive thrombocytosis (RT) is needed. Following recent developments in automated blood cell analyzers, various platelet indices can now be measured. In this study, we analyzed whether platelet counts and 6 platelet indices can be used for the differentiation of ET from RT in patients with a platelet count of 600x10(3)/microL or more. METHODS The subjects studied were 31 patients with ET and 224 patients with RT. The platelet counts, mean platelet volume (MPV), plateletcrit (PCT), platelet distribution width (PDW), mean platelet mass (MPM), mean platelet component concentration (MPC) and large platelets (LPLT) were measured by ADVIA 120 (Bayer Diagnostics, USA). The mean values of each item were compared between the two patient groups and the sensitivity and specificity of each item in the diagnosis of ET were determined by ROC curve analysis. RESULTS In essential thrombocythemia, all parameters except MPC were significantly higher than in reactive thrombocytosis. For the diagnosis of ET, the sensitivity and specificity were: 74.2% and 84.4%, when the platelet count was > or = 820 x 10(3)/microL; 80.6% and 80.0%, when the plateletcrit was > or = 0.63%; and 64.5% and 99.1%, respectively, when LPLT was > or = 23 x 10(3)/microL. CONCLUSIONS The platelet counts and platelet indices are useful for the differential diagnosis of thrombocytosis. The plateletcrit and LPLT are particularly useful for the diagnosis of ET when the platelet count is markedly increased.

Myelofibrosis is usually observed in association with hematologic malignancies or metastatic solid tumors, but it has rarely been reported in patients who suffer with autoimmune disorders. Autoimmune myelofibrosis is a distinct clinicopathologic entity and it can occur alone or in association with autoimmune disorders, and the final result is chronic peripheral cytopenia. Primary autoimmune myelofibrosis, in which the autoimmune myelofibrosis is not preceded by a well-defined autoimmune disease, has recently been defined as a distinct clinicopathologic syndrome. We report here on a case of an 18-year-old woman who was diagnosed with primary autoimmune myelofibrosis, and she manifested peripheral pancytopenia, positivity for autoantibodies and Grade III myelofibrosis without having any preceding autoimmune or hematologic disorders.