Hematogones: The Supreme Mimicker and a Cytomorphological Confounder in Acute Lymphoblastic Leukemia.

 B-lymphocyte progenitors, namely the hematogones (HGs), may pose problems in morphological assessment of bone marrow, not only during the diagnostic workup but also while evaluating bone marrow for remission status following chemotherapy. Here, we describe a series of 12 cases of acute lymphoblastic leukemia (ALL) that included both B-ALL and T-ALL cases, which were evaluated for remission status and revealed blast-like mononuclear cells in bone marrow in the range of 6 to 26%, which on immunophenotypic analysis turned out to be HGs.  This is a case series of 12 ALL cases who were undergoing treatment at the Army Hospital (Referral and Research), New Delhi. All these cases were under workup for post-induction status (day 28) and to check for suspected ALL relapse. Bone marrow aspirate (BMA), biopsy, and immunophenotyping were performed. Multicolored flow cytometry was performed using CD10, CD20, CD22, CD34, CD19, and CD38 antibodies panel.  BMA assessment of 12 cases revealed a maximum of 26% blastoid cells and a minimum of up to 6%, raising the suspicion of hematological relapse. However, on clinical assessment, these patients were well preserved, with preserved peripheral counts. Hence, marrow aspirates were subjected to flow cytometry using the CD markers panel, as discussed above, which revealed HGs. These cases were followed by minimal residual disease (MRD) analysis that revealed MRD-negative status, further confirming our findings.  This case series highlights the importance of morphology and bone marrow immunophenotyping in unveiling the diagnostic dilemma in post-induction ALL patients.