Paediatric Malignant Blue Cell Tumours- A Practical Pathological and Immunohistochemical Study in Duhok, Iraq

Abstract

Introduction: Malignant Blue Cell Tumours (MBCTs) are common heterogeneous tumours among paediatric age group. Their heterogeneity is reflected in their therapeutic and prognostic diversity. Mere morphology is not enough to differentiate them. Immunohistochemistry is a key tool for identification of small blue cell tumours that lack evidence of lineage differentiation on the ground of light microscopic morphology. Aim: To identify the immunohistochemical identity of paediatric MBCTs in Duhok, Iraq. Materials and Methods: This was a cross-sectional study performed on 120 cancers reported morphologically as MBCTs over 11-year period, from January 2009 to December 2019. Clinical data and histomorphologic acumen were considered and integrated with the immunohistochemical findings. Applying autostainer, immunohistochemistry was performed using monoclonal or polyclonal antibodies. Results: Lymphoma/leukaemia topped the diagnostic list 36 (30%) formed the commonest category, followed by Ewing’s/Primitive Neuro Ectodermal Tumour (PNET) 29 (24.2%), Neuroblastoma 16 (13.3%), Wilm’s tumour 11 (9.2%), Rhabdomyosarcoma 9 (7.5%) and Medulloblastoma 7 (5.8%). The remainders comprised Retinoblastoma (3.4%), Glioblastoma and Ependymoma (2.5% each). Hepatoblastoma and Astroblastoma formed the least frequent tumours (0.8% each). These tumours were more frequently located in the soft tissue (30%) followed by brain (14.2%), bone (10%), Lymph Node (LN) (9.2%) and kidney (10%). Conclusion: Integration of clinical data and histomorphologic acumen helped much for categorisation of MBCTs. Application of immunohistochemistry in this study has shown a significant improvement in the diagnostic accuracy of paediatric MBCTs. Loss of some differentiation antigens and aberrant expression of some markers often necessitate the use of panels of antibodies and, even molecular testing to target the task.