• Deauville five-point scale: A 1-to-5 score for how bright a lymphoma looks on PET compared with the liver; 1-3 is considered a complete metabolic response.
• R-CHOP (lymphoma chemoimmunotherapy): R-CHOP is the standard first treatment for diffuse large B-cell lymphoma: rituximab (an antibody against CD20) plus four chemotherapy drugs (cyclophosphamide, doxorubicin, vincristine, prednisone), given every three weeks for six cycles with curative intent.
• Indolent and aggressive lymphoma: Lymphomas are split by how fast they grow, and the split decides what happens next.
• Lugano classification / Ann Arbor staging: The Lugano classification is the lymphoma staging system: stage I to IV by how many lymph node regions and organs are involved, with PET-based response criteria.
• Radiotherapy in lymphoma: involved-site fields, 24 Gy, 4 Gy and total skin electron therapy: Lymphoma is one of the most radiation-sensitive cancers there is, so the doses are low and the fields are small.
• The two lymphoma classifications of 2022 (WHO-HAEM5 and ICC): Since 2022 there have been two reference classifications of lymphoma rather than one, published within months of each other by overlapping groups of experts.
• The lymphoma regimen alphabet: R-CHOP, pola-R-CHP, DA-EPOCH-R, ABVD, BEACOPP and the rest: Lymphoma treatment is written in acronyms, one letter per drug.

Making the diagnosis, and the trap in it: The diagnosis needs a generous biopsy, because the appearance varies across a single tumour and a core needle may sample only the part that looks like one of the neighbouring diseases. Both 2022 classifications require involvement of the mediastinum: an identical-looking tumour elsewhere in the body is diffuse large B-cell lymphoma, not otherwise specified. A nodular sclerosis classic Hodgkin lymphoma with variable CD20 expression remains Hodgkin lymphoma and is not reclassified here.

Biomarker results to ask for: A high density of tumour cells, which separates it from classic Hodgkin lymphoma, Strong expression of at least two B-cell markers (CD20, CD79a, PAX5), which the International Consensus Classification requires for the diagnosis, CD30 and often CD15, shared with classic Hodgkin lymphoma, Involvement of the mediastinum, which both 2022 classifications now require, Epstein-Barr virus, which is usually negative; an EBV-positive tumour with Hodgkin-like cells is classified as EBV-positive diffuse large B-cell lymphoma instead.

Scans and tests linked to this cancer: FDG PET, Histopathology & immunohistochemistry.

Bring copies of scan reports, pathology and blood results, and a list of every medicine and supplement.

• Treatment: Treated with regimens designed for aggressive large B-cell lymphoma and containing rituximab, rather than with Hodgkin lymphoma chemotherapy, because the tumour retains its B-cell programme and the surface target with it. Radiotherapy to the residual mediastinal mass is used in some series. There is no randomised trial in this entity, the published series number in the tens, and the regimen is chosen in a multidisciplinary meeting; the detail sits on the primary mediastinal B-cell lymphoma page and in the treatment layer of this family. (Primary mediastinal (thymic) large B-cell lymphoma, Rituximab, The lymphoma regimen alphabet: R-CHOP, pola-R-CHP, DA-EPOCH-R, ABVD, BEACOPP and the rest, Radiotherapy in lymphoma: involved-site fields, 24 Gy, 4 Gy and total skin electron therapy, R-CHOP (lymphoma chemoimmunotherapy))

From the standard of care recorded for this cancer; which apply depends on your stage and biomarkers. Ask which the team recommends and why.