Acute Biphenotypic Leukemia: Single Center Experience of Laboratory Presentation and Review of the Diagnostic Criteria.

Biphenotypic Acute Leukemia (BAL) is a rare, newly defined disease in the WHO classification of hematological neoplasms. There is little information about the laboratory presentation, and considerable difficulties exist in reaching a definite diagnosis. In this study, designed to examine the laboratory presentation of BAL, we report a total of 23 (3.4%) out of 676 adult and pediatric leukemia cases referred to our center during the last 4 years.

The mean age at presentation was (21.57 ± 15.59 years; range 1 year – 66 years). There were 14 males. The mean hematological and biochemical parameters were as follows: WBC 68.76 ± 65.18 x 10 ⁹/L, Hemoglobin 94.13 ± 15.13 g/L, Platelets 105.7 ± 104.23 x 10 ⁹/L, and LDH 1351.44 ± 1118.29 u/L. Fourteen patients (60.8%) had mixed morphology of small and large blast cells and seven were M1 and M2 according to FAB criteria.

Using the European Group for Immunological Classification of Leukemia (EGIL) scoring system, all patients had positive Myeloid markers with EGIL scores that ranged from 2.0 – 5.5. Eighteen patients were positive for B-cell markers with scores ranging from 2.0 – 8.5 but only 8 patients were positive for T-cell markers with scores of 0.5 – 4.0. Three patients were positive for markers of the three cell lines. In 7 patients myeloid lineage commitment was also demonstrable by ultrastructural myeloperoxidase. Five patients (22%) had normal cytogenetics. Philadelphia chromosome was positive by karyotype in 3 patients (13%) and MLL gene in 2 (8.7%). Three patients (13%) demonstrated trisomies involving chromosomes 19, 22 and 4, respectively.

Out of the 23 patients, 11 (48%) are alive without disease, 4 had died with leukemia, 3 are alive with disease and 5 had lost follow up.