Mr. Salim, a 62-year-old man, presented with right neck and left groin swelling for 3 months along with 7-8 kg of weight loss. Biopsy revealed diffuse large B-cell non-Hodgkin lymphoma (NHL). He was diagnosed with stage IV NHL and treated with rituximab and CHOP chemotherapy. The presentation discusses lymphadenopathy causes, lymphoma types and differences between Hodgkin and non-Hodgkin lymphomas, risk factors, investigations and treatments. Key points include distinguishing reactive from tumoral lymph nodes, indolent versus aggressive NHL subtypes, common genetic abnormalities in lymphomas, and involvement of Epstein-Barr virus in certain malignancies.