Lymph Node Biopsy
Lymph node biopsy removes all or part of an enlarged lymph node to find the cause of lymphadenopathy. It gives the pathologist tissue that keeps the node architecture, which is needed to diagnose and classify lymphoma, to distinguish infection from malignancy, and to find the origin of metastasis.
Three methods exist: excisional (the whole node removed through an incision), incisional (part of a large node or mass), and core needle biopsy. Fine needle aspiration is a cell sample, and it is covered by its own test. Excisional biopsy is the preferred method for suspected lymphoma because the architecture and cell mix are key for classification.
The procedure is done under local or general anaesthesia, and takes 20 to 60 minutes. The tissue is divided at the time of surgery for formalin fixation, flow cytometry, microbiology, cytogenetics and molecular tests. The final report takes 5 to 10 days, and longer with special tests.
Most enlarged lymph nodes are reactive or infective, and malignancy is found in about 1% of primary care patients with unexplained lymphadenopathy. The rate is higher with age, node size, and hard, fixed or supraclavicular nodes. Excisional biopsy gives a specific diagnosis in over 90% of cases that need it.
Indications.
- Persistent unexplained lymphadenopathy over 4 to 6 weeks that does not resolve.
- Node over 2 cm, hard, fixed, matted, rapidly growing, or in the supraclavicular fossa.
- Generalised lymphadenopathy with constitutional symptoms (fever, night sweats, weight loss).
- Suspected lymphoma, with imaging showing a mass or nodes.
- Suspected tuberculosis, sarcoidosis or other granulomatous disease.
- Metastasis of unknown primary, after aspiration or core biopsy has not given a diagnosis.
- Persistent lymphadenopathy in HIV infection, with suspected lymphoma, Kaposi sarcoma, Castleman disease or infection.
- Reclassification of a known lymphoma at relapse or transformation.
Not indicated for small (under 1 cm), soft, mobile nodes with an obvious cause, such as a nearby infection. Observation for 2 to 4 weeks is usual. It is also not the first step for suspected squamous cell carcinoma of the head and neck, where aspiration and endoscopy come first.
Contraindications and precautions.
- Bleeding disorder or anticoagulation that has not been managed.
- Large anterior mediastinal mass, or airway or vena cava compression: general anaesthesia and the supine position are dangerous, so local anaesthesia and sitting position are used, with anaesthetic and critical care advice.
- Do not give corticosteroids before biopsy when lymphoma is suspected, because they can shrink the tumour and make diagnosis difficult.
- Neck nodes in the posterior triangle lie close to the accessory nerve, and care is needed.
- Suspected germ cell tumour with inguinal nodes: do not biopsy through the scrotum.
- A node previously aspirated is acceptable, but a biopsy of a node with scarring may be less informative.
- Highly aggressive disease (Burkitt lymphoma) can cause tumour lysis, so supportive care is ready.
Preparation and technique.
The node most likely to give a diagnosis is chosen. This is the largest, most abnormal and most representative node, or the node with the highest uptake on PET-CT. Inguinal nodes are less useful because they are often reactive, and axillary and cervical nodes are preferred when there is a choice.
Blood tests (full blood count, clotting, HIV status) and imaging are reviewed. The skin is cleaned, local anaesthetic is infiltrated, and an incision is made over the node. The node is dissected out with its capsule intact, and handled gently, since crushing destroys the cells. Vessels are tied or clipped, and the wound is closed.
The fresh node goes to the laboratory without delay. The pathologist cuts it into slices, makes touch imprints, and sends tissue for formalin fixation, flow cytometry (in culture medium or saline), cytogenetics, molecular studies, frozen storage, and culture for bacteria, mycobacteria and fungi.
