Lymphoma
Lymphoma is a cancer of lymphocytes that arises in lymphoid tissue such as lymph nodes, the spleen, and mucosa-associated lymphoid tissue. It is divided into Hodgkin lymphoma and the much larger group of non-Hodgkin lymphomas.
Lymphomas are malignancies of B cells, T cells, or natural killer cells that grow as solid masses within lymphoid organs. This distinguishes them from leukemias, which are lymphoid or myeloid malignancies circulating primarily in the blood and bone marrow, although the two categories overlap when a lymphoma spreads into the marrow.
The classic presentation is painless lymphadenopathy — firm, rubbery, non-tender nodes that persist and enlarge. Roughly a third of patients also have B symptoms: unexplained fever, drenching night sweats, and weight loss exceeding 10% of body weight over six months. Diagnosis requires an excisional lymph node biopsy so that architecture, not just cell morphology, can be examined; staging uses imaging to determine how many node regions are involved and whether disease has crossed the diaphragm or reached extranodal sites.
Hodgkin lymphoma is defined histologically by Reed-Sternberg cells — large binucleated cells often described as having an owl-eye appearance — set in a reactive background of normal inflammatory cells. It has a bimodal age distribution, tends to arise in cervical or mediastinal nodes, and spreads contiguously from one nodal group to the next, which makes it comparatively amenable to localized therapy. Non-Hodgkin lymphomas are far more numerous and heterogeneous, ranging from indolent follicular lymphoma to aggressive diffuse large B-cell and Burkitt lymphomas. They spread noncontiguously, involve extranodal sites more often, and are more likely to be widely disseminated at diagnosis.
USMLE Step 1 tests lymphomas in the pathology of hematology and oncology, expecting you to recognize Reed-Sternberg cells, distinguish Hodgkin from non-Hodgkin patterns of spread, and connect specific subtypes with their characteristic translocations and viral associations. The CCMA exam covers lymphoma more briefly among diseases and disorders of the lymphatic system.
Key takeaways
- Lymphoma is a malignancy of lymphocytes that forms masses in lymph nodes and other lymphoid tissue.
- It usually presents as painless, firm lymphadenopathy, sometimes with B symptoms of fever, night sweats, and weight loss.
- Hodgkin lymphoma is identified by Reed-Sternberg cells and spreads contiguously between adjacent nodal groups.
- Non-Hodgkin lymphomas are more common and diverse, spread noncontiguously, and involve extranodal sites more often.