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

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.

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.

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).

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