Aberrant Expression of CD19 in Early T-cell Precursor Lymphoblastic Leukemia- A Diagnostic Challenge

A systematic approach is required to diagnose acute leukemia. Most of the cases are satisfactorily diagnosed and categorized into subtypes. However, a few cases pose diagnostic dilemma secondary to immunophenotypic aberrancies which are defined as antigens that are normally restricted to a different lineage and expressed by a neoplastic population while absent from its normal non neoplastic counterpart. We report a rare case of Early T-cell Precursor Lymphoblastic Leukemia with aberrant expression of CD19. A 7-year-old boy referred to our hospital with his cervical lymph node biopsy reported as lymphoproliferative disorder. The patient was COVID-19 positive. Chest X-ray showed mild right sided pleural effusion with huge mediastinal mass. Flow cytometry on peripheral blood used to establish the diagnosis. The case is reported to improve knowledge regarding aberrant expression of markers. Hematopathology teams should be aware of this phenomenon so that appropriate workup can be done to reach correct diagnosis.