Primary extranodal lymphomas: Five-year experience from a tertiary care center of North India.

Background: Primary extranodal lymphomas (pENL) are lymphomas with minimal nodal involvement and dominant extranodal disease. We aimed to study the prevalence and clinicopathological characteristics of pENL presenting at our center over 5 years from January 2015 to January 2020.

Methods: This is a cross-sectional study of pENL patients in which relevant clinical and laboratory data was collected including demography, site, stage, international prognostic index-revised, imaging findings, hematological, and biochemical parameters and comorbidities including underlying immunodeficiency. The paraffin blocks were subjected to routine hematoxylin and eosin stain and immunohistochemistry with standard lymphoma panel.

Results: Of 341 lymphomas, 73 (21.4%) were pENL with commonest site being gastrointestinal tract (31.5%) followed by head and neck (23.2%) and soft tissues (9.6%). Diffuse large B-cell lymphoma (DLBCL) (39.7%) was the commonest histological type (germinal center type-48%, nongerminal center-52%) followed by marginal zone lymphomas (MZL) (23.3%) and primary CNS lymphoma (8.2%). Primary breast lymphoma, primary bone marrow lymphoma, and follicular lymphoma constituted 4.1, 5.4, and 4.1% of pENL, respectively. There was a case of high grade B cell lymphoma of ileum with features intermediate between DLBCL and Burkitt. Other unusual pENL were anaplastic DLBCL of tonsils, DLBCLs of bone marrow with M band, MZL of base of tongue, Richter's transformation of tonsillar small lymphocytic lymphoma, and follicular lymphoma presenting as pericardial mass. Of 12 cases of T-non-Hodgkin lymphoma, commonest were mycosis fungoides (4/12) followed by mediastinal T-lymphoblastic lymphoma (2/12) and peripheral T-cell lymphoma (2/12).

Conclusion: pENL has unique clinical presentation depending on the location with site-specific distribution of histological subtypes.