Percutaneous (through skin) needle biopsy is a procedure that involves obtaining a small sample of a tissue. Biopsies considered as a common procedure performed by the radiologists.
This sample could be a tumor, lesion, or organ of interest. This includes any part of the body which can be accessed safely by percutaneous approach. Depending on the location, type of biopsy, the tools differ.
This is performed via a puncture of skin with a needle using image guidance. The most commonly used imaging guidance’s are Ultrasound and CT. Other modalities utilized for biopsy include MRI and Fluoroscopy (X ray’s), Sometimes there might be a need for combination of modalities like CT and Ultrasound.
There are two common techniques for PNB:
- Fine needle aspiration biopsy (FNAB)
- Core needle biopsy (CB)
Fine needle aspiration biopsy involves the use of a small hollow needle that is inserted into tissue to obtain cells for further evaluation.
The core needle biopsy involves the use of a special needle with an internal cutting mechanism that allows precise extraction of the desired piece of tissue.
There are lot of models, different designs, availability in different gauges and lengths.
There are two types of biopsies:
- Random biopsy
• Targeted biopsy
For example, Random liver biopsy is performed to look for a diffuse pathology or a targeted biopsy which is targeted at a lesion is performed to assess the nature of the lesion.
Examples for random include: Liver, Renal, bone and targeted include: Thyroid nodule, Lung nodule, Lymph node biopsies.
Reasons for a percutaneous needle biopsy include:
- Characterization of a lesion (e.g., benign versus malignant),
- Cancer staging, and
- Therapy guidance.
Contradictions to the procedure include:
- Lack of a safe needle pathway to the lesion,
- Severe bleeding disorders,
- Local changes
- Infection (low risk)
In addition, there is always a risk of inadequate samples due to various reasons requiring further attempts or different techniques to obtain the samples.
Where there is enough tissue and safer, Core biopsy is recommended as it will yield more tissue and there by more information.
Fine needle aspiration can be performed with or without local anesthetic while core needle biopsy is performed with local anesthetic and sedation (depending on the type of procedure).
Depending on the type of procedure and expertise, the risks varies and it is advisable to know from the operator or the institute where the procedure is performed.
For example, a liver biopsy can be uneventful most of the times, but there is always a risk of bleeding. Management of bleeding varies depending on the presentation and it ranges from conservative measures like bed rest to the extreme intervention like embolization or surgical intervention.