The lymphatic system is the body's primary defence against infection and spread of malignant cells. It consists of the spleen, tonsils, thymus, lympnode, lymph vessels and the lightly yellow fluid called lymph.
A lymph node biopsy is a procedure in which a part of a lymph node or the entire node is removed to make the diagnosis of a disease and assess progression of a disease. A normal lymph node is about 1.3cm in diameter. Lymph nodes harbouring infection or malignant cells may be larger than this.
Lymph nodes are found in specific locations such as in the neck, in the axilla or in the inguinal area, where they can be examined by palpation easily; in other, deep lying locations such as in the abdomen along the big arteries and veins they can be assessed only by special investigations such as ultrasound or computerised tomography. In situations such as these, a radiologist may be asked to do sonar or CT guided biopsy of the lymph node.
Three types of lymph node biopsies are common:
- Fine needle aspiration
Fine needle aspiration (FNA) is a technique that allows a biopsy of various lumps including lymp nodes. It allows one to retrieve cells for microscopic analysis and thus make a diagnosis of a number of problems, such as inflammation or even cancer. It is performed as an office procedure and requires no special preparation.
A small needle is inserted into the mass. Negative pressure is created in the syringe, and as a result of this pressure difference between the syringe and the mass, material can be drawn into the syringe. The needle is moved in a to-and-fro fashion, obtaining enough material to make a diagnosis. This procedure is generally accurate and frequently prevents the patient from having an open, surgical biopsy, which is more painful and costly. The procedure generally does not require anaesthesia. It is about as painful as drawing blood from the arm for laboratory testing (venipuncture). In fact, the needle used for FNA is smaller than that used for venipuncture. Although not painless, any discomfort associated with FNA is usually minimal.
No medical procedure is without risks. Due to the small size of the needle, the chance of spreading a cancer or finding cancer in the needle path is non-existent. Other complications are rare; the most common is bleeding. If bleeding occurs at all, it is generally seen as a small bruise. Patients who take aspirin, Advil® or Coumadin®, are more at risk of bleeding. However, the risk is minimal. Infection is extremely rare after FNA.
- Open lymph node biopsy
This is mainly done on patients whose fine needle aspiration has yielded indeterminate results. It can be done for both superficial and deep nodes depending on the general condition of the patient. This is frequently the case in lymphomas (blood cancers) or, in cases of HIV infection for suspected intra-abdominal tuberculosis, when no peripheral nodes could be found.
The procedure is usually done in a day theatre under local or general anaesthesia and normal preparations for surgery apply. Using antiseptic solution, the area for the biopsy is cleaned and draped. An incision is made in the line of the skin crease and the lymph node is dissected out and sent for histology. The wound is closed and pain tablets prescribed. Depending on the site of the biopsy, complications such as nerve injuries (neck), lymphatic fluid leak (inguinal) or vascular injuries (abdominal) may occur, but generally are rare.
- Sentinel lymph node biopsy
This is done to establish regional lymph node status and to determine the adjuvant therapy in cancer management, mainly for breast cancer and melanoma, a pigmented skin cancer. It also helps to give prognostic information and planning for regional control of the disease.
Sentinel lymph node biopsy looks for the first node that filters fluid draining away from the cancer.
The day before the operation, a radioactive isotope is injected into the site where the cancer is located. With a special gamma camera uptake into lymph nodes is recorded. This is called "lymph node mapping" as it makes the pathways along which the cancer spreads, visible. On the day of surgery, in theatre, under general anaesthesia, 1-2ml of isosulfan blue dye is injected at the tumour site. The dye also drains to the sentinel node and marks the sentinel nodes by discolouring it blue. A handheld gamma probe is used to locate the node for the biopsy. After removal of the node the node is for the presence of malignancy; if malignancy is found in the node, a removal of all nodes in the area, commonly known as a "block dissection", is performed.