Clinicopathological Analysis of Plasmablastic Lymphoma Cases: A Cross-sectional Study from a Tertiary Care Cancer Centre in Kerala, India

Introduction: Plasmablastic Lymphoma (PBL) is an aggressive lymphoid neoplasm composed of large atypical B cells with plasmablastic or immunoblastic morphology and a terminal B-cell differentiation phenotype predominantly presenting at extranodal sites. PBL is rare comprising 1% of large B-cell lymphomas. Most PBLs occur in the context of immune deficiency/dysregulation. Aim: To analyse the morphology, immunophenotype, clinical details and diagnostic challenges in cases diagnosed as PBL. Materials and Methods: The present study was a crosssectional cohort study analysing cases of PBL diagnosed during 2011 to 2021 in the Department of Pathology, Regional Cancer Centre, Thiruvananthapuram, Kerala, India. Morphology and Immunohistochemistry (IHC) (CD45, CD3, CD5, CD20, CD79a, Pax5, CD38, CD138, MUM1, EMA, Kappa, Lambda, CD56, CD30, Alk-1, Ki-67) of tumour cells were reviewed. Epstein-Barr Virus (EBV) by Rapid in Situ Hybridisation (RISH) was also documented. Clinical details including patients age, sex, clinical presentation were elaborated using descriptive statistics. Treatment details and overall survival also noted. Results: During the study period there were a total of 36 cases. The median age at presentation was 57 years (range: 10 to 85 years). Six cases (16.7%) had associated HIV, 26 cases (72.2%) had extranodal disease. Tumour cells in all cases were positive for CD138 and MUM1, and negative for CD20, PAX5, and T-cell markers with a high Ki-67 proliferation index (80-95%). Leukocyte Common Antigen (LCA) were negative in 22 cases (61.11%) or weakly positive in 14 cases (38.9%), CD 79a was faintly positive in one case (2.8%) and weak Pax5 positivity was seen in two cases (5.6%). EBV was positive in 21 cases (58.3%) Median overall survival was 17.5% for 3-year in the present study. Conclusion: PBL is a rare aggressive lymphoma having association with HIV, predominant extranodal location, and characteristic IHC pattern. Lymphoproliferative neoplasms with plasmablastic morphology share many morphologic and immunophenotypic similarities and diagnosis requires integration of clinical morphological and IHC findings.