When diffuse large B-cell lymphoma is limited to one area of the body—known as stage I—early and accurate diagnosis becomes the foundation for successful treatment and the best possible outcomes.
Introduction: Who Should Undergo Diagnostics and When
People who notice unusual changes in their body should consider seeking medical evaluation, especially when these changes persist for several weeks. The most common sign that prompts someone to visit a doctor is a lump or swelling that does not go away and appears to be getting larger. These swellings typically appear in areas where lymph nodes—small structures that filter germs and help fight infection—are located, such as the neck, armpits, or groin. The lump is usually painless, though in some cases it may cause discomfort.[1]
About three out of ten people with diffuse large B-cell lymphoma experience what doctors call “B symptoms.” These include a high fever above 103 degrees Fahrenheit that lasts longer than two days or comes and goes without an obvious cause, unexplained weight loss of more than 10 percent of total body weight over six months, and heavy night sweats so intense they drench the sheets. Having these symptoms does not automatically mean someone has lymphoma, but they are important warning signs that should not be ignored.[1]
Diffuse large B-cell lymphoma is a fast-growing cancer, which means symptoms can start or worsen within just a few weeks. Because the cancer develops quickly, early diagnosis is especially important. Anyone experiencing painless swellings in lymph node areas, unexplained fevers, significant weight loss, or drenching night sweats should contact a healthcare provider promptly. The sooner the condition is identified, the better the chances of successful treatment.[3]
In some cases, diffuse large B-cell lymphoma can grow in places other than lymph nodes. When it develops in the stomach or bowel, it might cause abdominal pain, diarrhea, or bleeding. If it grows in the chest, it might lead to breathlessness or a cough. These symptoms can be confusing because they mimic other common health problems, which is why it is important to see a doctor if they persist or worsen.[3]
Diagnostic Methods: Identifying the Disease
The journey toward a diagnosis of diffuse large B-cell lymphoma often begins with a physical examination. During this exam, a healthcare provider checks for swollen lymph nodes in the neck, underarms, and groin. They also feel for an enlarged spleen or liver, which can be signs that the lymphoma has spread to these organs. This initial examination helps the doctor determine which additional tests are needed.[9]
The most important test for diagnosing lymphoma is a biopsy, which involves removing a sample of tissue for examination under a microscope. For diffuse large B-cell lymphoma, doctors usually perform a lymph node biopsy, removing all or part of a swollen lymph node. If lymphoma is suspected in other parts of the body based on symptoms or initial test results, a biopsy sample may be taken from those areas as well. In the laboratory, specialists look at the cells to see if they are cancerous and, if so, what type of cancer they represent.[9]
Under the microscope, diffuse large B-cell lymphoma has a distinctive appearance. The cancer cells are larger than normal, healthy B cells, and they are spread out—or diffuse—throughout the tissue rather than grouped together. This characteristic pattern is what gives the disease its name and helps doctors distinguish it from other types of lymphoma.[3]
Blood tests play an important supporting role in the diagnostic process. These tests can sometimes show whether lymphoma cells are present in the bloodstream. Blood tests are also used to check for viruses that may be associated with lymphoma, including Epstein-Barr virus, HIV, hepatitis B, and hepatitis C. Additionally, blood tests measure the level of lactate dehydrogenase (LDH), a substance that is often higher in people with lymphoma. Elevated LDH levels can suggest more widespread disease.[9]
Once lymphoma is confirmed through a biopsy, doctors use imaging tests to see where the cancer is located and how much of the body it affects. Imaging tests create pictures of the inside of the body, allowing doctors to visualize tumors and enlarged lymph nodes. Common imaging tests include CT scans (computed tomography), MRI scans (magnetic resonance imaging), and PET scans (positron emission tomography). These scans help determine the stage of the lymphoma, which is essential for planning treatment.[9]
A PET-CT scan is particularly useful because it combines two types of imaging in one test. The PET portion shows areas of high metabolic activity, which often indicates cancer, while the CT portion provides detailed anatomical images. This combination helps doctors see exactly where the lymphoma is located and how active it is. PET scans have improved the accuracy of both staging and restaging, meaning doctors can better assess the disease at diagnosis and monitor how well treatment is working.[11]
To determine if lymphoma has spread to the bone marrow, doctors may recommend a bone marrow biopsy. Bone marrow is the soft tissue inside bones where blood cells are made. The procedure involves using a needle to collect samples of both the liquid and solid parts of the bone marrow, usually from the hip bone. These samples are examined in a laboratory to check for the presence of lymphoma cells.[9]
If there is concern that lymphoma might have spread to the brain or spinal cord, a doctor may perform a lumbar puncture, also called a spinal tap. During this procedure, a small amount of the fluid that surrounds the brain and spinal cord is collected with a needle. The fluid is then tested for lymphoma cells. An MRI scan of the head or spine may also be done to look for lymphoma in the central nervous system.[3]
All of these tests work together to give doctors a complete picture of the disease. The combination of physical examination, biopsy, blood tests, imaging studies, and sometimes bone marrow or spinal fluid analysis allows healthcare providers to confirm the diagnosis, understand the extent of the disease, and plan the most appropriate treatment strategy for each individual patient.
Staging: Understanding the Extent of Disease
After diagnosis is confirmed, doctors determine the stage of the lymphoma, which describes how much cancer is present in the body and where it is located. Staging is crucial because it helps guide treatment decisions. All lymphomas, including diffuse large B-cell lymphoma, are staged using the same system, which ranges from stage 1 to stage 4.[6]
In stage 1, only one lymph node or group of lymph nodes in one area of the body is affected. This is considered early-stage disease. Stage 2 means that more than one group of lymph nodes is involved, but all of them are on the same side of the diaphragm—the muscle that separates the chest from the abdomen. Stage 3 indicates that lymph nodes on both sides of the diaphragm contain lymphoma. Stage 4, the most advanced stage, means the lymphoma has spread to other organs beyond the lymph nodes, such as the lungs, liver, or bone marrow.[6]
Doctors also add letters to the stage number to provide more detailed information about the disease. The letter “B” indicates that the person has B symptoms—fever, night sweats, and significant weight loss. If these symptoms are not present, the letter “A” is used. The presence of B symptoms can affect both the prognosis and the treatment plan.[6]
Staging also considers the size of swollen lymph nodes and whether the lymphoma is described as “bulky,” meaning there are large masses of cancer. All of this information helps doctors predict how the disease might behave and what treatment approach will be most effective.[6]
Diagnostics for Clinical Trial Qualification
When patients are considered for enrollment in clinical trials, additional diagnostic tests may be required beyond those used for standard diagnosis and staging. Clinical trials are research studies that test new treatments or combinations of treatments, and they often have specific criteria that patients must meet in order to participate.
One common requirement is detailed genetic and molecular testing of the lymphoma cells. Researchers have identified more than 70 different genetic mutations linked to diffuse large B-cell lymphoma, and understanding which mutations are present in an individual patient’s cancer can help match them to appropriate clinical trials. Some trials are designed specifically for patients whose lymphoma has certain genetic features.[14]
Clinical trials may also require specific imaging tests at baseline, such as a PET-CT scan, to establish a clear picture of the disease before treatment begins. This allows researchers to accurately measure how well the experimental treatment is working by comparing images taken before and after treatment.
Blood tests are often repeated more frequently in clinical trial settings to monitor not only the disease but also how the body is responding to the new treatment. These tests help ensure patient safety and provide valuable data about the treatment’s effects.
Patients interested in participating in clinical trials should discuss with their healthcare team what additional tests might be needed. The specific requirements vary depending on the trial, but the goal is always to gather enough information to safely and effectively evaluate the new treatment being studied.



