Follicular lymphoma is a slow-growing cancer of the immune system that starts in white blood cells called B cells. It is the most common type of indolent (slow-growing) non-Hodgkin lymphoma, with about 2.4 new cases per 100,000 people each year in the United States. The median age at diagnosis is 64, though it can occur earlier.
How Follicular Lymphoma Develops
Your immune system produces B cells in lymph nodes, where they mature inside structures called germinal centers. In follicular lymphoma, a genetic error causes these B cells to survive far longer than they should. In up to 90% of cases, a piece of chromosome 18 swaps places with a piece of chromosome 14. This swap turns on a protein that normally stays quiet, one that blocks the cell’s built-in self-destruct program. Instead of dying off naturally, the defective B cells accumulate, forming tumors in lymph nodes and sometimes spreading to bone marrow, the spleen, or other organs.
The cancer cells still look and behave somewhat like the germinal center cells they came from. They tend to grow in a circular, follicle-like pattern under the microscope, which is where the name comes from.
Common Signs and Symptoms
The most typical first sign is painless swelling of one or more lymph nodes, often in the neck, armpits, or groin. Because the disease grows slowly, many people have it for months or even years before noticing anything unusual. Swollen nodes may come and go on their own, which can delay diagnosis.
Some people also develop what doctors call “B symptoms”: drenching night sweats, unexplained fevers, or unintentional weight loss of more than 10% of body weight over six months. These symptoms tend to appear when the disease is more advanced or more active. Fatigue is another common complaint, sometimes caused by the lymphoma crowding out healthy blood cells in the bone marrow.
How It Is Diagnosed
A diagnosis requires a biopsy, usually of an enlarged lymph node. Imaging alone or a needle aspirate isn’t enough because pathologists need to see the tissue architecture to distinguish follicular lymphoma from other types of lymphoma.
Under the microscope, the biopsy is tested with a panel of markers that identify the cancer cells’ origin. The cells are positive for CD20 (a protein on B cells), CD10, and BCL6 (both markers of germinal center origin). They also overexpress BCL2, the survival protein driven by the chromosome swap. This combination of markers, along with the follicular growth pattern, confirms the diagnosis.
Grading
Pathologists grade the lymphoma based on how many large, aggressive-looking cells (centroblasts) appear among the smaller cancer cells. Grade 1 and 2 tumors are mostly small cells with few centroblasts and behave in a slow-growing, indolent fashion. Grade 3A has a higher proportion of large cells but still contains small cells mixed in. Under the most recent WHO classification, grades 1 through 3A are grouped together as “classic follicular lymphoma.”
Grade 3B is different. It consists almost entirely of large cells and behaves more like an aggressive lymphoma. The newest WHO guidelines actually renamed it “follicular large B-cell lymphoma” to reflect that distinction, and it is treated more aggressively.
Staging
Once diagnosed, imaging (typically a PET/CT scan) and sometimes a bone marrow biopsy determine how far the disease has spread. Staging follows the Lugano classification:
- Stage I: Cancer in one lymph node group or one area outside the lymph system
- Stage II: Two or more lymph node groups on the same side of the diaphragm
- Stage III: Lymph node groups on both sides of the diaphragm, or nodes above the diaphragm plus spleen involvement
- Stage IV: Cancer has spread to organs beyond the lymph system, such as bone marrow or liver
Most people are diagnosed at stage III or IV because the disease is so slow-growing that it has time to spread before causing noticeable symptoms. A late stage does not carry the same urgent implications it would for many other cancers, because follicular lymphoma often responds well to treatment even when widespread.
Watch and Wait vs. Active Treatment
One of the most surprising things for newly diagnosed patients is that treatment doesn’t always start right away. If the disease is low-volume and not causing symptoms, doctors often recommend active surveillance, sometimes called “watch and wait.” This means regular checkups and imaging, with treatment held in reserve until it’s needed.
The decision to start treatment is guided by specific criteria that assess tumor burden. The most widely used set, the GELF criteria, flags patients for treatment if they have any tumor mass larger than 7 cm, three or more affected lymph node sites each larger than 3 cm, B symptoms, significant spleen enlargement, fluid buildup in the chest or abdomen, or blood count problems caused by bone marrow involvement. If none of these triggers are present, waiting is a safe and evidence-supported strategy that avoids the side effects of treatment without compromising long-term outcomes.
First-Line Treatment Options
For limited-stage disease (stage I or early stage II), radiation therapy to the affected area can be highly effective and is sometimes the only treatment needed. Some patients remain in remission for years after radiation alone.
When treatment is needed for more advanced disease, the standard approach combines an antibody therapy that targets CD20 on the cancer cells with chemotherapy. The three most common combinations are:
- Bendamustine plus rituximab (BR): Often preferred for its favorable balance of effectiveness and tolerability
- R-CHOP: Rituximab combined with a four-drug chemotherapy regimen, used for decades with strong track records
- R-CVP: A somewhat gentler chemotherapy combination with rituximab, sometimes chosen for older patients or those with other health conditions
After completing initial treatment, many patients continue rituximab alone every two to three months as maintenance therapy to prolong remission. Most people respond well to first-line treatment, though the disease is considered incurable with standard therapy because it tends to relapse over time.
Treatment for Relapsed Disease
When follicular lymphoma returns after initial treatment, there are now several newer options beyond repeating chemotherapy. Two categories of immunotherapy have received FDA approval for patients who have had at least two prior treatments.
CAR-T cell therapy involves collecting your own immune cells, genetically engineering them in a lab to recognize and attack the lymphoma, and infusing them back. Three CAR-T products are approved for relapsed follicular lymphoma. This is a one-time treatment that requires a hospital stay and close monitoring for side effects, but it can produce deep, durable remissions.
Bispecific antibodies are a newer class of drugs that work by physically bridging your immune cells to the cancer cells, forcing them into close contact so the immune system can destroy the lymphoma. Two bispecific antibodies, mosunetuzumab and epcoritamab, are FDA-approved for relapsed follicular lymphoma. Epcoritamab received its approval in June 2024. These are given as injections and are generally easier to administer than CAR-T therapy.
Transformation Risk
One of the more serious concerns with follicular lymphoma is the possibility that it transforms into a faster-growing cancer, most commonly diffuse large B-cell lymphoma (DLBCL). In one long-term study of 281 patients, 13% experienced this transformation, with rates reaching about 15% at 10 years and 26% at 14 years. After that point, the risk appeared to plateau.
Transformation typically happens within the first few years, at a median of about 2.75 years from the original diagnosis. Signs that may signal transformation include rapidly enlarging lymph nodes, new B symptoms, or a sharp rise in certain blood markers. Transformed lymphoma is treated aggressively, similar to DLBCL, and carries a worse prognosis than follicular lymphoma that remains indolent. This risk is one of the key reasons doctors monitor patients closely even during watch-and-wait periods.
Outlook and Survival
Follicular lymphoma has one of the better prognoses among blood cancers. While it is generally considered incurable with conventional therapy, many people live with it for decades, cycling through periods of treatment and remission. Advances in immunotherapy over the past two decades have meaningfully improved outcomes, and the recent approval of CAR-T and bispecific antibody therapies has added new options for patients whose disease returns. The overall trajectory for most people with follicular lymphoma is one of a chronic, manageable condition rather than an immediately life-threatening one.