Diagnosing Non-Hodgkin's Lymphoma requires a great deal of skill, and an expert pathologist. Below are just some of the tests and technologies that may be used to achieve a correct diagnosis. Click on the menu items below for some more detailed information on various diagnostic procedures.
One emerging technology is "high throughput sequencing" It is a way of detecting circulating tumour DNA (ctDNA) or circulating tumour cells (CTC) in the blood with nothing more than a blood test (3) (4). Sometimes you will hear this referred to a a liquid biopsy. This technology is new, it is expensive and not routinely used. But due to its simplicity it will eventually become far more widespread.
How often have you heard that wise old advice, "Get a second opinion"? Well that is very good advice, but what many people don't realize is that the second opinion you need most of all is from another pathologist. (1) It is the pathologist who determines exactly what you have, not your haematologist or oncologist. Since your treatment depends on what you have you need to be certain you have been diagnosed properly before your doctor can recommend any treatment. That brings up a second dilemma. Lymphoma comes in over 60 different varieties and sometimes it is extremely difficult to be sure which variety you have. It is not at all uncommon for two different pathologists to give two different diagnosis. Fortunately the treatment as often as not is going to be the same, but that still doesn't lessen the importance of knowing for sure just exactly what you have. Here we will try to explain some of the tests you may undergo to determine exactly what type of NHL you have.
Please note though that not all the tests discussed below are performed on every patient. When Lymphoma is suspected then every patient will undergo some routine tests such as blood work and a physical exam. In the end though, it is only through a biopsy of a suspected tumour that you can be entirely certain.
This is probably the first test that they will do. The problem though is that you cannot diagnose lymphoma by a blood test. All you can do is review the results and see if "something" appears to be wrong. Lymphoma circulates within the lymph system and not the blood system so detecting lymphoma by a simple blood test is extremely unlikely. What they can detect however is abnormal blood counts which simply gives them a clue to look for a cause. Since lymphoma is a cancer of the lymphocytes (a type of white blood cell) you might think that a high lymphocyte count would be a strong indicator of lymphoma, but it is not. A high lymphocyte count in the blood is more likely to indicate an infection or maybe even leukaemia which is a cousin to lymphoma because it is also a cancer of the white blood cells. The difference is that in leukaemia the cancerous blood cells are found primarily in the blood and marrow, whereas lymphoma is found primarily in the lymph and marrow.
Another number they will look at when doing a blood test is the Lactate Dehydrogenase count. LDH is a combination of 5 different normal isoenzymes found in the blood. The level of LDH can go high in reaction to many different kinds of stress or damage to body tissues. As tissues are damaged they release more LDH. For example heart attacks will cause a high LDH counts within hours of the attack. Nevertheless active cancer activity can elevate them as it stresses and damages the surrounding body tissues. Although an LDH test isn't very useful for an initial diagnosis of lymphoma it is frequently used as monitoring test for those who already have lymphoma. Any elevation from the normal range may indicate a relapse or renewed growth.
Traditionally only an actual biopsy of tumour tissue could definitively diagnose lymphoma (see below) But in recent years research has shown that small bits tumour DNA actually circulates in the blood. Using high tech DNA sequencing techniques they can detect this DNA, and not only tell what type of lymphoma it is, but through examining the mutations they can predict the prognosis. They may also be able to determine what chemotherapy drugs will be most effective and least effective. This technology is very new and not ready for the clinic just yet. But it is not so far down the road. You will sometimes hear this referred to a "liquid biopsy". Below are articles about the technology and the results they have achieved so far.
Curently the only true way to diagnose lymphoma is to do a biopsy of the suspect tumour/tissue. Nothing else will do, although as noted above circulating DNA may change this in the near future. This means removing a lymph node or section of a tumour and examining it under a microscope by an experienced pathologist. Actually a haematopathologist (one who specializes in pathology of the blood/lymph systems). The most common way to do this is a surgical procedure to literally cut it out and examine it. This is easy enough if the swollen node are near the surface of the skin, such as neck, armpit, or groin nodes) The problem is that some tumour masses are deep inside the body where it would be inconvenient at best, and risky at worst to cut the patient open and remove the node. Sometimes they will attempt what is called a Fine Needle Aspiration, or Needle biopsy for short. This means inserting a large needle (under lots of sedation of course) into the body and cutting out a chunk of the mass they are interested in. The problem with this procedure is that it has a very low rate of success. Most test results come back inconclusive. This procedure is used most often when they want to avoid major surgery to open up the body cavity just to get a good sample.
Bone marrow biopsies are routinely done at diagnosis but are used less often for regular follow up. In this procedure the doctor will insert a large needle into to large marrow producing hip bones. He will then extract a bit of the marrow, then follow that up by cutting out a small piece of the bone. Just like a tissue biopsy, the bone marrow sample will be examined under a microscope to look for signs of lymphoma and diagnose what type it is. Recent studies are starting to show that, at least for aggressive lymphomas, a PET scan can detect bone marrow involvement more accurately. This may eliminate the need for painful bone marrow biopsies. (2)
Having bone marrow involvement is very common for non-Hodgkin's lymphoma, and it is of less significance than you might expect. As a general rule lymphoma in the marrow will respond to treatment just as well as lymphoma in any other body part.
Bone marrow biopsies can be a very uncomfortable and painful experience for some people. Yet for others it is not painful at all. Some say it is the doctors technique that makes the difference, others say it is the patients ability to tolerate pain, and yet others say it is the medications you take that make the difference. Every patient will receive one of the freezing agents such as xylocaine to freeze the area. For most people including this webmaster who has had about twenty BMB's, this is all that is required for pain management. The key is to use lots of freezing. (My doctor uses 20cc of xylocaine).
Then there are three other types of medication that are used as needed.
It is best to discuss what pain control measures will be used with your doctor before the procedure begins.
These three types of scans are very useful tools for detecting and monitoring a wide variety of diseases including lymphoma. It must be understood first and foremost that none of these scans can "diagnose" lymphoma. They can only detect abnormal masses, or activity in the body. Your doctor will use many different tests and procedures to diagnose you and these are just three of the tools he might use.
Immunohistochemistry is the method by which they can examine the cells and determine what antigens are expressed on the surface of the cells by using antibodies that bind to those antigens. They can also determine how strongly those antigens are expressed. This is a standard procedure which helps the pathologist determine the type of lymphoma with far greater accuracy than just examining the biopsy under the microscope. A chart of which antigens are typically positive or negative is on our CD marker chart. CD marker is just another term for antigens, where the CD stands for Cluster of Differentiation A full discussion of how Immunochemistry works is beyond the scope of this web site, but here is a link to an excellent (though technical) introduction to immunochemistry.
Although Flow Cytometry has been around for long time, it is only in the past decade that they technology has really advanced dramatically. It gives scientists a way to separate and examine individual cells and detect various properties they are interested in, including lymphoma. For those with some of the more aggressive types of lymphoma it means they can sometimes detect residual disease long before it grows large enough to be detected by any other means. The simple explanation is that they are able to pass a stream of cells one at a time, through a beam of laser light. This laser light can measure their size and separate the cells by size. Cells are then tagged with a fluorescent dye and another laser is used to excite them. The ones that are fluoresced can then be separated, either for counting and analysis or for growing more of that type of cell. The great benefit is that by examining the cells one by one they can find the most minute quantities of what they are looking for. Here are two links you should check out if you want some more detailed information about Flow cytometry.
For the patient, it is important to understand that Flow Cytometry is an advanced technology that is not performed on every biopsy sample. Pathologists have a variety of tools and advanced diagnostic methods at their disposal, and flow cytometry is just one of them.