{"entity":{"id":"primary-effusion-lymphoma","kind":"cancer","name":"Primary effusion lymphoma","aka":["PEL","Body cavity-based lymphoma","Extracavitary primary effusion lymphoma","KSHV/HHV8-associated lymphoma","HHV8-positive primary effusion lymphoma"],"tldr":"A rare lymphoma that grows as fluid rather than as a lump: it fills the space around the lungs, the heart or the bowel without forming a mass. It is caused by Kaposi sarcoma herpesvirus and arises mostly in people with advanced HIV infection, and it is diagnosed by sending the fluid itself for testing.","summary":"What it is. A large B-cell lymphoma driven by Kaposi sarcoma herpesvirus, also called human herpesvirus 8, the same virus that causes Kaposi sarcoma. The lymphoma cells float free in a body cavity and produce fluid: a pleural effusion around the lung, a pericardial effusion around the heart, or ascites in the abdomen. Classically there is no tumour mass at all, which is why the diagnosis is made on the fluid.\n\nHow it differs from the lymphomas around it. WHO-HAEM5 groups it in a family of conditions caused by the same virus: multicentric Castleman disease, germinotropic lymphoproliferative disorder, primary effusion lymphoma, its extracavitary form, and KSHV/HHV8-positive diffuse large B-cell lymphoma. The classification acknowledges that the boundaries between them are not clean, that individual patients overlap, and that difficult cases should be settled in a multidisciplinary meeting rather than by rule. In particular, telling a lymph node-based extracavitary primary effusion lymphoma from a KSHV/HHV8-positive diffuse large B-cell lymphoma can be arbitrary; the International Consensus Classification prefers the latter diagnosis where Epstein-Barr virus is negative and the tumour expresses IgM lambda.\n\nThe lymphoma it is most often confused with, and the 2022 change that separates them. There is a second disease that also presents as lymphoma confined to a body cavity, in older people without immune deficiency who have heart failure, kidney failure or cirrhosis causing fluid to accumulate. It is not caused by Kaposi sarcoma herpesvirus, its cells look like ordinary mature B cells rather than plasmablasts, and it behaves considerably better. WHO-HAEM5 made it a separate entity in 2022, calling it fluid overload-associated large B-cell lymphoma; the International Consensus Classification calls it primary effusion-based lymphoma that is negative for both viruses, and lists it as provisional. Distinguishing the two matters because the outlook is different.\n\nWho gets it. Most often a person with advanced, often undiagnosed, HIV infection; it also occurs after organ transplant and in older people from regions where Kaposi sarcoma herpesvirus is common, including parts of the Mediterranean and sub-Saharan Africa. In people with HIV the tumour usually carries Epstein-Barr virus as well; in older HIV-negative people it usually does not.\n\nHow it is diagnosed and treated. The fluid is drained and sent for cell counts, cytology, flow cytometry and immunohistochemistry or in situ hybridisation for the virus. The cells are large and plasmablastic, usually lacking the B-cell markers (CD20 is typically negative) and carrying plasma cell markers instead, which is why anti-CD20 antibodies have no role. Treatment is combination chemotherapy together with full antiretroviral therapy where there is HIV; the regimens, which have never been compared in a randomised trial, sit in the treatment layer of this family and on the HIV-associated lymphoma page.","asOf":"2026-09-29","wikipedia":"https://en.wikipedia.org/wiki/Primary_effusion_lymphoma","links":[{"label":"WHO Classification of Haematolymphoid Tumours, 5th edition: lymphoid neoplasms (Alaggio, Leukemia 2022)","url":"https://doi.org/10.1038/s41375-022-01620-2"},{"label":"International Consensus Classification of Mature Lymphoid Neoplasms (Campo, Blood 2022)","url":"https://doi.org/10.1182/blood.2022015851"},{"label":"Trends in incidence and survival of patients with primary effusion lymphoma in the United States, a population-based cohort study of 236 patients (Hematological Oncology 2026)","url":"https://doi.org/10.1002/hon.70168"},{"label":"NCI PDQ: adult non-Hodgkin lymphoma treatment (health professional version)","url":"https://www.cancer.gov/types/lymphoma/hp/adult-nhl-treatment-pdq"}],"tags":["heme","lymphoma","subtype-page"],"related":["hiv-associated-lymphoma","dlbcl","plasmablastic-lymphoma","non-hodgkin-lymphoma","kaposi-sarcoma"],"cancers":[],"sections":[],"technologies":["histopathology-ihc"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["hhv8-kshv","ebv-term","lymphoma-classification-2022","lymphoma-nodal-versus-extranodal","oncogenic-viruses"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"group":"haematologic","burden":"In the United States, 236 adults were recorded in the SEER registries between 2001 and 2021, with a median age of 51 years and 88 per cent of them men. The age-adjusted incidence rose from 1.0 to 1.6 cases per ten million person-years between the first and second halves of that period. Five-year relative survival improved from 21 to 37 per cent across the same two periods, and median overall survival from 4 to 12 months, which the authors attribute to advances in both lymphoma treatment and HIV care.","subtypes":["Classic primary effusion lymphoma, confined to a body cavity, which is an extranodal site with no mass","Extracavitary primary effusion lymphoma, which forms a mass with the same biology"],"biomarkers":["Kaposi sarcoma herpesvirus (human herpesvirus 8) in the tumour nuclei, by immunohistochemistry for the latency-associated nuclear antigen; this is the diagnosis","Epstein-Barr virus, usually positive in people with HIV and usually negative in older people without","A plasmablastic phenotype: CD45 positive, CD20 and CD79a usually negative, CD138 and MUM1 positive","HIV status, which changes the whole of the management","Absence of the virus, which moves the diagnosis to fluid overload-associated large B-cell lymphoma and changes the outlook"],"standardOfCare":[{"setting":"Making the diagnosis on the fluid","approach":"The effusion is drained and sent, fresh, for cytology, flow cytometry and immunohistochemistry. The diagnosis requires the Kaposi sarcoma herpesvirus latency-associated nuclear antigen in the tumour nuclei. A cavity lymphoma without the virus is a different disease, recognised separately in 2022, that arises in fluid overload from heart failure, kidney failure or cirrhosis and behaves better. HIV testing is part of the work-up in every case.","refs":["hhv8-kshv","ebv-term","histopathology-ihc","lymphoma-classification-2022"],"guideline":{"version":"WHO Classification of Haematolymphoid Tumours, 5th edition (2022), with the International Consensus Classification (2022) where they differ","url":"https://doi.org/10.1038/s41375-022-01620-2"}},{"setting":"Treatment","approach":"Combination chemotherapy, with antiretroviral therapy started or optimised at the same time where there is HIV, because controlling the HIV is part of controlling the lymphoma. Anti-CD20 antibodies have no role: the cells do not carry CD20. There has never been a randomised trial in this entity and the regimens come from series and from the HIV-associated lymphoma literature; they sit in the treatment layer of this family and on the HIV-associated lymphoma page. Entry into a trial is a reasonable first choice rather than a last resort.","refs":["hiv-associated-lymphoma","cyclophosphamide","doxorubicin","etoposide","lymphoma-tx-regimen-alphabet"],"guideline":{"version":"NCI PDQ: adult non-Hodgkin lymphoma treatment","url":"https://www.cancer.gov/types/lymphoma/hp/adult-nhl-treatment-pdq"}}],"stateOfArt":[],"history":[{"year":1995,"title":"Kaposi sarcoma herpesvirus found in body cavity lymphomas","note":"The virus discovered in Kaposi sarcoma the year before was found in a group of lymphomas that grew in body cavities without forming a mass, which defined the disease.","refs":[]},{"year":2022,"title":"Separated from the lymphoma it most resembles","note":"WHO-HAEM5 made fluid overload-associated large B-cell lymphoma a separate entity: the same presentation in an older person with heart, kidney or liver failure, without the virus, with a mature B-cell rather than plasmablastic phenotype, and with a better outlook.","refs":["lymphoma-classification-2022"]},{"year":2026,"title":"A population picture, and survival that has improved","note":"Across 236 United States patients diagnosed between 2001 and 2021, five-year relative survival rose from 21 to 37 per cent and median overall survival from 4 to 12 months between the first and second halves of the period.","refs":["hiv-associated-lymphoma"]}],"pipeline":[],"openProblems":["There has never been a randomised trial in primary effusion lymphoma, and median overall survival in the most recent population series was 12 months.","The boundaries between the conditions caused by Kaposi sarcoma herpesvirus are acknowledged by the classification itself to be unclear, and individual patients overlap between them.","The commonest route to this diagnosis is advanced, undiagnosed HIV infection, which is a failure of testing rather than of oncology."],"parent":"non-hodgkin-lymphoma"},"route":"/cancers/primary-effusion-lymphoma/","neighbours":{"cancer":[{"id":"dlbcl","kind":"cancer","name":"Diffuse large B-cell lymphoma","route":"/cancers/dlbcl/"},{"id":"hiv-associated-lymphoma","kind":"cancer","name":"HIV-associated (AIDS-related) lymphomas","route":"/cancers/hiv-associated-lymphoma/"},{"id":"kaposi-sarcoma","kind":"cancer","name":"Kaposi sarcoma","route":"/cancers/kaposi-sarcoma/"},{"id":"non-hodgkin-lymphoma","kind":"cancer","name":"Non-Hodgkin lymphoma (all types)","route":"/cancers/non-hodgkin-lymphoma/"},{"id":"plasmablastic-lymphoma","kind":"cancer","name":"Plasmablastic lymphoma","route":"/cancers/plasmablastic-lymphoma/"}],"technology":[{"id":"histopathology-ihc","kind":"technology","name":"Histopathology & immunohistochemistry","route":"/technologies/histopathology-ihc/"}],"term":[{"id":"ebv-term","kind":"term","name":"Epstein-Barr virus (EBV) in cancer","route":"/terms/ebv-term/"},{"id":"hhv8-kshv","kind":"term","name":"HHV-8 (KSHV) status and LANA-1 immunohistochemistry","route":"/terms/hhv8-kshv/"},{"id":"lymphoma-nodal-versus-extranodal","kind":"term","name":"Nodal and extranodal lymphoma","route":"/terms/lymphoma-nodal-versus-extranodal/"},{"id":"lymphoma-tx-regimen-alphabet","kind":"term","name":"The lymphoma regimen alphabet: R-CHOP, pola-R-CHP, DA-EPOCH-R, ABVD, BEACOPP and the rest","route":"/terms/lymphoma-tx-regimen-alphabet/"},{"id":"lymphoma-classification-2022","kind":"term","name":"The two lymphoma classifications of 2022 (WHO-HAEM5 and ICC)","route":"/terms/lymphoma-classification-2022/"}],"pathway":[{"id":"oncogenic-viruses","kind":"pathway","name":"Oncogenic viruses","route":"/pathways/oncogenic-viruses/"}],"drug":[{"id":"cyclophosphamide","kind":"drug","name":"Cyclophosphamide","route":"/drugs/cyclophosphamide/"},{"id":"doxorubicin","kind":"drug","name":"Doxorubicin","route":"/drugs/doxorubicin/"},{"id":"etoposide","kind":"drug","name":"Etoposide","route":"/drugs/etoposide/"}]}}