Lymph nodes play a crucial role in the body’s immune system, filtering substances and housing white blood cells that fight infection. Sometimes, these lymph nodes become enlarged, a condition known as lymphadenopathy. While often a sign of infection, enlargement can also occur due to a variety of other causes, including a condition called follicular hyperplasia (FH). Understanding FH, its causes, and how it differs from more serious conditions like lymphoma is important for both patients and healthcare providers.
What is Follicular Hyperplasia?
Follicular hyperplasia is a type of lymphoid hyperplasia, meaning an abnormal increase in the number of lymphoid follicles within lymph nodes. It’s a reactive process, meaning it’s a response to a stimulus, rather than an intrinsic problem with the lymph node itself. Specifically, FH involves stimulation of B cells, a type of white blood cell responsible for producing antibodies. This stimulation leads to the growth of secondary follicles within the lymph node’s cortex – the outer layer – without disrupting the overall structure of the node.
The follicles in FH are often described as polymorphous, meaning they vary in size and shape. This contrasts with the more uniform appearance of follicles in certain types of lymphoma.
Symptoms of Follicular Hyperplasia
Lymphadenopathy associated with follicular hyperplasia can present with a range of symptoms, though these are not specific to FH and can occur with many other conditions. These may include fever, chills, night sweats, and unexplained weight loss. More localized symptoms, such as swelling, pain, warmth, and tenderness, can also be present in the affected lymph node area. Lymph nodes can range in size from small, pea-sized lumps to larger, golf ball-sized swellings.
Causes of Follicular Hyperplasia
Several conditions can trigger follicular hyperplasia. These include:
- Rheumatoid arthritis: An autoimmune disease causing inflammation of the joints.
- Sjögren syndrome: Another autoimmune disorder affecting moisture-producing glands.
- IgG4-related disease: A condition characterized by elevated levels of IgG4 antibodies and inflammation in various organs.
- Kimura disease: A rare chronic inflammatory disorder.
- Toxoplasmosis: An infection caused by a parasite.
- Syphilis: A sexually transmitted infection.
- Castleman disease: A rare disorder involving an overgrowth of lymphoid tissue.
- Progressive transformation of germinal centers (PTGC): A reactive lymphoproliferative process.
- Microorganisms: Infections caused by viruses and bacteria can also lead to inflammation and lymphoid hyperplasia.
Distinguishing Follicular Hyperplasia from Follicular Lymphoma
A key concern when evaluating lymph node enlargement is differentiating between reactive processes like follicular hyperplasia and lymphoma, a cancer of the lymphatic system. Follicular lymphoma specifically shares a similar name and microscopic appearance with FH, making accurate diagnosis crucial.
The critical distinction lies in the cellular characteristics of the enlarged lymph node. Follicular hyperplasia is polyclonal, meaning the B cells within the follicles originate from multiple different cell lines. In contrast, follicular lymphoma is monoclonal, meaning the cells arise from a single, abnormal cell line. FH does not typically express the bcl-2 protein, while follicular lymphoma does.
Lymphoma-Like Lesions in Women
In some cases, particularly in women of reproductive age, a condition called lymphoma-like lesions (LLL) can occur in the lower female genital tract. These lesions present with a dense lymphoid infiltrate that can mimic lymphoma. However, LLLs are typically superficial, show surface erosion, and lack the deep invasion or prominent sclerosis seen in true lymphoma. Interestingly, even with molecular testing, some LLL cases show clonal rearrangement of the immunoglobulin heavy chain gene, which can initially suggest lymphoma, but often resolve without further intervention.
Diagnosis and Treatment
Diagnosing follicular hyperplasia typically involves a lymph node biopsy, where a sample of tissue is examined under a microscope. Immunohistochemical staining can help determine the clonality of the B cells and the presence or absence of bcl-2 protein.
Treatment for FH focuses on addressing the underlying cause. For example, if the hyperplasia is triggered by an infection, treating the infection will often resolve the lymph node enlargement. In cases related to autoimmune diseases, managing the autoimmune condition is the primary goal. There is no specific treatment for FH itself; the condition typically resolves once the stimulus is removed. Immunotherapy may be used to treat infections causing the condition.
It’s important to remember that any persistent or unexplained lymph node enlargement should be evaluated by a healthcare professional to determine the underlying cause and ensure appropriate management.
