Core Needle Biopsy
Core needle biopsy removes thin cylinders of tissue through a cutting needle, usually 14 to 18 gauge. Each core is 1 to 2 mm wide and 10 to 20 mm long. The core keeps the tissue architecture, so the pathologist can type and grade a tumour, judge invasion, and run immunohistochemistry and molecular tests.
It is done through the skin under image control (ultrasound, CT, MRI or mammography), or by palpation for superficial masses. Common targets are the breast, liver, kidney, prostate, lung, thyroid, lymph nodes, soft tissue, bone and retroperitoneal masses. It is also the main method for diagnosing diffuse organ disease in the liver and kidney.
The procedure takes 15 to 45 minutes, and observation afterwards lasts from 1 to 6 hours, depending on the organ. Local anaesthesia is used, and sedation is added for anxious patients and deep targets.
A diagnostic result is obtained in most biopsies of a suspicious mass. A minority are non-diagnostic because of sampling error, necrosis or a small sample. Breast core biopsy has a sensitivity of about 97 to 99% and a specificity close to 100% for cancer when the lesion is sampled correctly.
Indications.
- A mass or infiltrate needing histological diagnosis before treatment.
- Tumour typing, grading and receptor or molecular testing (breast, lung, prostate, soft tissue).
- Lymphoma suspected in a node or mass, when excision is not possible.
- Diffuse parenchymal disease: persistent abnormal liver tests, nephrotic syndrome, unexplained renal impairment, and transplant dysfunction.
- Suspicious imaging findings: breast calcification or mass, thyroid nodule with an equivocal aspirate, bone lesion.
- Metastasis of unknown primary.
- Confirmation of malignancy before major surgery or chemotherapy.
Not indicated when the result will not change management, when imaging is typical of a benign lesion that needs no treatment (for example, a haemangioma of the liver), or when a safe route to the lesion does not exist.
Contraindications and precautions.
- Uncorrected bleeding disorder, platelet count under about 50 x 10⁹/L, or an INR over about 1.5 for deep organ biopsy. Limits depend on the organ and local practice.
- Anticoagulants and antiplatelet drugs need a plan for stopping and restarting, based on bleeding risk of the site and thrombotic risk of the patient.
- Uncooperative patient or one who cannot lie still or hold the breath.
- Infection at the entry site.
- Vascular lesions, cystic hydatid lesions and lesions next to major vessels need specialist planning.
- Single functioning kidney, severe emphysema or pulmonary hypertension (lung biopsy), and uncontrolled hypertension (renal biopsy).
- Pregnancy: ultrasound control is preferred over CT.
Preparation and technique.
Consent is taken, the site and side are checked, and the platelet count, coagulation tests and medicine list are reviewed. Blood pressure is controlled before renal biopsy. Fasting is used if sedation is planned.
The patient is positioned for the safest route, for example supine for the liver, prone for the kidney, and supine or prone for the lung. The skin is cleaned and draped, and lidocaine is infiltrated to the capsule.
A coaxial introducer allows several cores through a single entry. The needle is advanced under real time image control to the edge of the target, the cutting mechanism is fired, and the core is withdrawn. Usually 3 to 6 cores are taken, with more for prostate (a systematic scheme of 10 to 12 plus targeted cores) and for renal disease (two cores, to allow light microscopy, immunofluorescence and electron microscopy).
Cores go into 10% neutral buffered formalin without delay. Fresh tissue is set aside when lymphoma, infection, renal immunofluorescence or special studies are possible. The track may be plugged or compressed, and the patient is observed with regular pulse and blood pressure checks.
