Lymphoma

Lymphoma is a malignancy of lymphocytes, the immune cells that normally move through lymph nodes, spleen, bone marrow, blood, and extranodal tissues. That distribution explains why lymphoma may present as enlarged nodes, a mediastinal mass, splenomegaly, marrow-related cytopenias, or disease in organs outside the lymphatic system. The first major distinction is Hodgkin lymphoma (HL) versus non-Hodgkin lymphoma (NHL). They are not simply two stages of the same disease. Their biology, pathology, prognosis, and treatment plans differ. Classical Hodgkin lymphoma (cHL) arises from germinal-center B cells and is defined by malignant Reed-Sternberg cells. These large malignant cells typically express CD30 and CD15 but lack CD20 and CD45. A striking pathology feature is that Reed-Sternberg cells are only a small fraction of the tumor. Most of the enlarged node is a reactive inflammatory environment of lymphocytes, eosinophils, macrophages, and other immune cells recruited around the malignant cells. This helps explain why a person with cHL may have prominent systemic symptoms despite relatively few malignant cells. The inflammatory background produces cytokine-driven fever, fatigue, pruritus, and night sweats. Do not treat all Hodgkin lymphoma...