The abbreviation Bx stands for biopsy. This procedure involves the precise removal of a small sample of tissue or cells from a living body for laboratory examination. A biopsy serves as the definitive method for diagnosing a wide range of diseases, allowing physicians to confirm a diagnosis at the cellular level, moving beyond visual observations or imaging studies.
Defining the Medical Term Biopsy
A biopsy is the removal of cells or a small piece of tissue from an area of concern for microscopic examination by a specialist called a pathologist. This procedure is generally performed when medical imaging, such as an X-ray, CT scan, or MRI, identifies an abnormal mass or suspicious change that requires further investigation. Imaging can reveal the location and size of an abnormality, but it cannot reliably differentiate between benign (non-cancerous) and malignant (cancerous) cells.
The primary purpose of a biopsy is to provide absolute cellular-level confirmation of a disease process, which is often required before any treatment plan can be established. Although most commonly associated with cancer diagnosis, biopsies are also routinely used to identify and characterize inflammatory conditions, infectious diseases, and autoimmune disorders. Obtaining this tissue specimen is the only way to establish a conclusive diagnosis by studying the cellular architecture and composition.
Methods for Collecting Biopsy Samples
The method used to collect a biopsy sample is selected based on the tissue’s location, size, and accessibility within the body. One of the least invasive methods is Fine-Needle Aspiration (FNA), which uses a very thin, hollow needle and a syringe to draw out fluid and a small cluster of cells from a mass, such as a lymph node or a thyroid nodule. A more substantial sample is obtained with a Core Needle Biopsy, utilizing a larger, spring-loaded needle to extract a cylindrical column of tissue, preserving the tissue structure for better analysis.
For masses deep inside the body, needle biopsies are often guided precisely by real-time imaging like ultrasound or computed tomography (CT) scans to ensure the correct target is sampled. When a skin lesion is the concern, a Punch Biopsy is frequently performed, using a circular cutting tool to remove a small, full-thickness disc of skin, including the epidermis and dermis.
To sample tissues lining internal organs, like the colon or stomach, an Endoscopic Biopsy is performed using a flexible tube (endoscope) inserted through a natural opening, which is equipped with a camera and tiny grasping tools. Finally, a surgical approach may be necessary: an Excisional Biopsy, where the entire suspicious mass is removed, or an Incisional Biopsy, where only a representative part of the larger mass is surgically cut out.
Laboratory Analysis and Results
Once the tissue sample is collected, it is immediately transferred to a pathology laboratory for processing and examination. The first step involves fixation, where the tissue is preserved, often using formalin, to prevent cellular degradation and maintain its structure. The fixed tissue is then dehydrated and embedded in a solid block of paraffin wax, which provides a firm support structure for subsequent sectioning.
A specialized instrument called a microtome is used to cut the paraffin-embedded block into extremely thin slices, typically only four to five micrometers thick. These delicate tissue ribbons are then mounted onto glass slides and stained to make the cellular structures visible under a microscope. The standard staining technique is Hematoxylin and Eosin (H&E), a two-part process that provides stark contrast.
Hematoxylin is a basic dye that stains acidic components, like the cell nuclei, a purplish-blue color, while Eosin is an acidic dye that stains the cytoplasm and extracellular matrix shades of pink. This contrast allows the pathologist, a doctor specializing in disease diagnosis through tissue examination, to clearly visualize the cellular architecture and look for any abnormal patterns, such as disorganized cell growth or invasion. The pathologist’s final interpretation of these microscopic findings is compiled into a detailed biopsy report, which provides the definitive diagnosis, indicating whether the cells are benign, malignant, or indicative of another specific condition.