A biopsy is a procedure to remove a small sample of tissue or cells from the body for examination under a microscope. Two common, minimally invasive methods are Fine-Needle Aspiration (FNA) and core needle biopsy. While both use a needle to collect material from a suspicious area, they differ in their approach, the type of sample acquired, and the diagnostic information they provide. A healthcare provider recommends one procedure over the other based on these differences.
Understanding Fine-Needle Aspiration (FNA)
Fine-Needle Aspiration (FNA) uses a very thin, hollow needle connected to a syringe to withdraw fluid and cells from a lump or mass. The needles used for an FNA are often smaller than those used for drawing blood. During the procedure, which takes only a few minutes, the needle is inserted into the targeted area to collect a sample of individual cells and small tissue fragments. This process may be repeated to ensure an adequate sample is collected for analysis.
The fine needle makes FNA a minimally invasive procedure that causes less discomfort than other biopsy methods. It is performed in an outpatient setting, sometimes without local anesthesia. The collected sample is spread on a glass slide, stained, and examined by a pathologist in a process called cytology, which focuses on individual cells. FNA is used to evaluate easily accessible abnormalities like thyroid nodules, swollen lymph nodes, and certain lumps in the breast or salivary glands.
Understanding a Core Needle Biopsy
A core needle biopsy uses a larger, hollow needle to extract one or more small, cylindrical pieces of tissue from a suspicious area. This method provides a more substantial sample than an FNA, capturing cells and their arrangement within the tissue. To perform the procedure, a local anesthetic is used to numb the area. Imaging techniques like ultrasound or mammography are often used to guide the needle precisely to the target.
The needle is inserted through a small nick in the skin and into the mass. A specialized device is often attached to the needle, which rapidly projects it into the tissue to collect a core sample. This process is repeated to obtain enough tissue for a thorough evaluation. The collected tissue cores are sent to a lab for histological analysis, where a pathologist examines the tissue architecture. This analysis is useful for diagnosing conditions in solid organs like the breast, prostate, or liver.
Key Differences and Deciding Factors
The choice between an FNA and a core biopsy depends on the type of sample needed for an accurate diagnosis. FNA collects individual cells for cytological review, which is sufficient for many conditions. A core biopsy retrieves a solid piece of tissue for histological examination of its structure. This architectural information is often necessary for a definitive diagnosis, especially in oncology.
For example, histology from a core biopsy helps a pathologist distinguish between in-situ and invasive cancers. While an FNA is less invasive, a core biopsy yields more tissue, which leads to higher diagnostic accuracy for complex solid masses. A core biopsy is therefore the preferred method for suspicious breast lumps.
A physician’s decision also considers the location and nature of the abnormality. For easily accessible, fluid-filled cysts or certain thyroid nodules, the information from an FNA may be sufficient. An FNA might be performed as an initial diagnostic step due to its less invasive nature and lower cost. If the results are inconclusive, a core needle biopsy may be recommended as a follow-up to gather more detailed information.