The lymphatic system is a network of vessels and organs that plays a major role in the body’s immune defense. Lymph nodes are small, bean-shaped glands scattered throughout this system that function as filters, trapping bacteria, viruses, and abnormal cells from the fluid circulating in the body called lymph. A lymph node biopsy is a medical procedure in which a surgeon or radiologist removes all or part of a lymph node or a tissue sample from it. This collected sample is then sent for laboratory analysis to determine the presence or absence of disease.
The Diagnostic Purpose of the Procedure
A physician orders a lymph node biopsy to investigate lymphadenopathy (unexplained or persistent lymph node enlargement). While often a temporary reaction to a minor infection, a swollen node that does not resolve requires microscopic analysis to rule out serious conditions. The procedure helps diagnose various infectious diseases, such as tuberculosis, or systemic inflammatory conditions.
The biopsy is frequently used in cancer care for both diagnosis and staging. For patients suspected of having lymphoma, a cancer originating in the lymphocytes within the nodes, the biopsy provides the definitive diagnosis. It also determines if cancer originating elsewhere has spread to the lymphatic system (metastasis). This information is used to determine the stage of the disease and guide treatment decisions.
Types of Lymph Node Biopsies
The method chosen depends on the node’s location, the amount of tissue needed, and the suspected diagnosis.
Fine-Needle Aspiration (FNA)
The least invasive approach is a Fine-Needle Aspiration (FNA) biopsy, which uses a needle to withdraw a small amount of fluid and cells directly from the node. This quick procedure is often performed in a doctor’s office, but it may not provide enough tissue to analyze the node’s overall architecture.
Core Needle Biopsy
A Core Needle Biopsy uses a slightly larger needle to extract a small, cylindrical piece of intact tissue. This larger sample allows the pathologist to examine the structure of the tissue, offering more diagnostic information than an FNA alone. Both FNA and Core Needle biopsies are often guided by imaging, such as ultrasound or CT scans, to ensure accurate needle placement.
Open Surgical Biopsy
When a larger tissue sample is required, an open surgical biopsy is performed. An excisional biopsy involves surgically removing the entire lymph node through a small incision. An incisional biopsy removes only a portion of a very large lymph node or mass. These surgical procedures provide the most material for analysis and are sometimes necessary to accurately diagnose complex lymphomas.
Sentinel Lymph Node Biopsy
This specialized approach is used for staging cancers like melanoma or breast cancer. It identifies the sentinel node, which is the first lymph node to receive drainage from the area where a tumor is located. A tracer, which can be a radioactive substance or a blue dye, is injected near the tumor site to map the lymphatic pathway to this specific node. The surgeon then removes the identified sentinel node to check for the presence of cancer cells.
Patient Preparation and Post-Procedure Care
Before a lymph node biopsy, patients are asked about their medication history, especially the use of blood thinners like aspirin or warfarin, to reduce the risk of bleeding. If the biopsy requires general anesthesia or sedation, patients will be instructed to fast beforehand.
Following the procedure, patients may experience discomfort or swelling at the biopsy site. For pain management, over-the-counter medication like acetaminophen is recommended, and patients should avoid non-steroidal anti-inflammatory drugs (NSAIDs). Patients who had a surgical biopsy must avoid strenuous activities or heavy lifting for about a week to prevent stress on the incision site.
The biopsy site must be monitored for signs of infection, including:
- Redness
- Warmth
- Swelling
- Fever
- Abnormal drainage
If a blue dye was used during a sentinel node biopsy, the skin and urine may temporarily appear blue or green for a few days. Most lymph node biopsies are performed on an outpatient basis.
Interpreting the Biopsy Results
After the sample is collected, it is sent to a pathology laboratory where a pathologist examines the tissue. The pathologist prepares the sample by thinly slicing and staining it to view the cellular structure. They look for abnormal cell structures, patterns of inflammation, or the presence of foreign cells, such as cancer or infectious agents.
To gain further detail, the sample may undergo specialized tests, such as immunohistochemistry and immunophenotyping. Immunohistochemistry uses antibodies to identify specific proteins on the surface of the cells, which helps determine the exact type of cancer or identify the origin of a metastatic cancer cell. The final pathology report will classify the findings as either “benign” or “malignant,” indicating the presence of cancer.
A benign result often means the node is “reactive,” signifying an immune response to a local infection or inflammation. A malignant result specifies whether the cancer originated in the lymph node itself (lymphoma) or if it is a metastatic cancer that spread from a primary tumor elsewhere. The report also details the number of nodes involved and the degree of cancer cell differentiation.