Needle Biopsy and the Dangers of Metastasis
What is Biopsy?
A biopsy is removal of some tissue from the body for examination, for the purpose of diagnosing a condition. There are various types of biopsies, viz. needle biopsy, excision biopsy, incision biopsy, wedge biopsy, etc. Needle biopsy is a frequently performed procedure, usually done when a condition is suspected to be malignant or the type of malignancy is to be determined.
What is Needle Biopsy?
Needle biopsy is an office procedure. No preparation is needed before undergoing the procedure. Patients who find it difficult to relax might be given a mild tranquilizer before the procedure begins. The area is cleaned with an antiseptic. A needle biopsy involves inserting a hollow needle into a suspected tumor to get samples for microscopic examination. It is a convenient, bloodless, virtually pain free procedure. It is also more cost effective and less invasive than open biopsy. Needle biopsies are of two types:
- Fine needle aspiration (FNA) - In this procedure, the doctor uses a very thin needle attached to a syringe to aspirate a small amount of tissue from a suspicious area. A local anesthetic may or may not be used because the needle used is thinner than that used for blood collection. This tissue is looked at under a microscope.
- Core needle biopsy - In core needle biopsy, a slightly larger hollow needle is used to withdraw small cylinders or cores of tissue from a suspected area. A local anaesthetic is used in this case as the needle is larger in size and the process is more invasive. It also removes more tissue than fine needle aspiration and hence the results are more definite.
The tissue removed by needle biopsy is preserved in formalin and sent for pathological examination. An antiseptic cream is applied over the wound and a gauze and adhesive tape is applied which is to be removed the next day.
Possible Metastatic Dangers of Needle Biopsy
Cells undergo many mutations and reproduce uncontrollably before turning cancerous. They also lose the orderliness and adhesiveness of normal tissue and travel outside the primary site, a phenomenon termed ‘metastasis’. Due to loss of cohesion between cells, it is sometimes easy to dislodge cancer cells from a tumor during biopsy. The metastatic dangers of needle biopsy are twofold:
- Like other cells in the body, cancer cells also have small blood vessels called capillaries which drain into veins and thus are connected to the blood stream. They are also bathed in tissue fluid which is connected to the lymphatic system. Inserting a needle into the tumor for biopsy involves the risk of dislodging a tumor cell into a blood vessel or into the tissue fluid.
- Tumour cells which enter into the blood vessels can travel to distant sites whereas those which enter into the tissue fluid go to lymph nodes. Some tumor cells may also be dragged along the route of the needle and hence lead to local implantation. This is known as implantation metastasis. This carries the risk that a tumor which previously could have been cured by resection may spread and thus palliative treatment may only be possible. This also means that the patient has to take combinations of chemotherapy with its dangerous and unpleasant side effects.
It is still not known clearly whether fine needle or core needle biopsy involves a higher risk of metastasis. It has been concluded from studies that a needle biopsy may increase the spread of the cancer by 50% as compared to excisional biopsies.
The Bottom-line
Thus needle biopsy should be performed only when tumors are inoperable and a diagnosis is necessary. In case of operable lesions, a wide excision biopsy is to be preferred.
To minimize the metastatic dangers of needle biopsy, the tunnel followed by the needle should be removed surgically in the next surgery.
The alternatives for needle biopsy can be imaging techniques like CT scan, PET scan,MRI or ultrasound. But these procedures also carry the risk of transient doses of radiation.
A new non-toxic diagnostic test is thermography which uses infrared radiation. It can serve as an adjunct to mammography to determine whether a lesion is benign or malignant in case of breast mass. The sensitivity of this procedure is 99%, and could well turn out to be an alternative for needle biopsy, atleast in certain cases.