Immunophenotypic characteristics of T lineage acute lymphoblastic leukemia: absence of immaturity markers-TdT, CD34 and HLADR is not uncommon.

INTRODUCTION

T ALL may show variable morphological features and immunophenotypic analysis for characterisation of immature nature of these cells is needed to establish a diagnosis and distinguish from reactive conditions and mature T cell leukemias. Sometimes immaturity markers-CD34, TdT and HLA DR may not be expressed by blasts. The aim of the present study was to analyse immunophenotype of T ALLs especially with respect to absence of immaturity markers.

METHODS

Thirty-eight cases of T ALL diagnosed over a period of two and half years were analysed retrospectively with respect to clinical features, haematological features and flow cytometric immunophenotyping for T, B, Myeloid and immaturity markers. Student's -test was used for comparing quantitative data and Chi-square test/Fishers exact -test for qualitative variables. value less than 0.05 was considered significant.

RESULTS

The most common T-lineage marker expressed was cCD3 and CD7 which were expressed in 100% cases followed by CD5 in 86.8% cases. The most common immaturity marker expressed was TdT (39.5% cases) followed by CD34 (34.2% cases). Thirteen cases (34.2%) were negative for all three of the immaturity markers i.e. TdT-/CD34-/HLADR. Absence of CD34 was associated with absence of expression of HLA DR (P<0.05) and aberrant expression of B lineage markers (P<0.05).

CONCLUSION

T-ALL is a rare and aggressive disease. Many cases lack immaturity markers viz, TdT, CD34 and HLADR. In such cases a comprehensive approach taking into account the clinical presentation, cytomorphology and immunophenotyping is diagnostic in experienced hands. Further, molecular studies may be needed to aid diagnosis.