Biopsy is a medical procedure in which a sample of tissue or cells is obtained from the body for examination, most commonly by pathology specialists. The term can refer to both the sampling procedure and the resulting specimen. Biopsies are used when direct examination of tissue architecture or cellular characteristics is needed to establish, confirm or classify a disease. They are particularly important in diagnosing cancers, inflammatory disorders, infections and many conditions where imaging or blood tests cannot provide sufficiently specific information. Unlike a blood test, which measures circulating material, a biopsy can reveal how cells are arranged within the actual affected tissue.
Several forms of Biopsy exist, selected according to the anatomical site, suspected condition and required amount of tissue. A needle biopsy uses a needle to remove cells or tissue, with fine-needle aspiration obtaining relatively small cellular samples and core biopsy obtaining a cylindrical tissue fragment. An incisional biopsy removes part of a lesion, while an excisional biopsy removes an entire accessible lesion when clinically appropriate. Endoscopic procedures can obtain tissue from internal organs, and skin biopsies can use techniques such as punch, shave or excisional sampling. The method is chosen to obtain diagnostically useful material while minimising unnecessary injury.
Biopsy specimens are usually examined using histopathology, in which tissue is processed, sectioned and stained so that cells and tissue architecture can be examined microscopically. Additional techniques may include immunohistochemistry, which detects specific proteins within cells or tissues, and molecular tests that identify genetic or other biological characteristics. In cancer diagnosis, pathology can establish tumour type, grade and other features relevant to classification and treatment. Some specimens undergo cytology rather than conventional tissue histology when only individual cells or small clusters are obtained. The distinction between cytology and histology reflects the amount and organisation of material available for examination.
Biopsy is often used after another investigation has identified an abnormality that requires clarification. Imaging can locate a mass or abnormal region but may not reliably determine whether it is malignant, inflammatory, infectious or benign. A biopsy can provide direct evidence of tissue characteristics and therefore sometimes represents the definitive diagnostic step. However, sampling error is possible because a small specimen may not represent the entire lesion. A non-diagnostic biopsy does not necessarily prove that a disease is absent; it may instead indicate that the specimen was insufficient, unrepresentative or technically unsuitable.
The procedure can be performed under local anaesthetic, sedation or general anaesthesia depending on the site and complexity. Imaging such as ultrasound, computed tomography or endoscopic guidance can improve targeting of lesions that cannot be located accurately by palpation. Potential complications depend on the anatomical location and procedure and can include bleeding, infection, pain or injury to nearby structures. The risk-benefit assessment considers the diagnostic value of obtaining tissue against procedural risks. Anticoagulant treatment and bleeding disorders may require specific management before some biopsies.
Pathology laboratories use careful specimen identification, fixation, processing and quality-control procedures because diagnostic interpretation depends on preserving tissue structure and molecular characteristics. Formalin fixation is widely used for many histological specimens, while certain investigations require fresh, frozen or specially preserved material. The pathology report can contain descriptive findings, diagnostic classification, grading and other features relevant to management. For complex diseases, specialist review or multidisciplinary discussion may be appropriate, particularly when treatment depends on subtle morphological or molecular distinctions.
Biopsy differs from screening and imaging because it directly samples biological material from the suspected site. It also differs from aspiration, although aspiration can be a form of biopsy when the objective is to obtain diagnostic cells or tissue. A biopsy does not automatically mean that cancer is suspected, although cancer diagnosis is one of its most familiar uses. Biopsies are also performed for conditions such as inflammatory bowel disease, liver disease, kidney disorders, skin diseases and certain infections. The decision to biopsy depends on the clinical question and whether the information gained is likely to change diagnosis or management.
The major strength of Biopsy is its ability to provide direct morphological and molecular evidence, but it is not infallible. Sampling limitations, processing artefacts, ambiguous findings and diseases with patchy distribution can complicate interpretation. Modern pathology increasingly combines microscopic examination with immunological and molecular techniques, making tissue specimens valuable sources of highly detailed diagnostic information. Nevertheless, biopsy findings must be interpreted alongside clinical history and imaging because tissue morphology can be nonspecific and because the meaning of a microscopic finding depends on its anatomical and clinical context.
