Biopsy: Types and What to Expect

A biopsy is the removal of tissue or cells from the body for examination under a microscope by a pathologist. It is the definitive method for confirming or ruling out cancer, providing information that imaging and blood tests alone cannot supply. This page covers the major biopsy classifications, the procedural steps involved in each, the clinical situations that call for specific approaches, and the criteria clinicians use when selecting one method over another.

Definition and scope

A biopsy produces a tissue or cell sample that a pathologist evaluates to determine whether abnormal, precancerous, or malignant cells are present. The National Cancer Institute (NCI) defines a biopsy as "the removal of cells or tissues for examination by a pathologist." That examination — described in detail on the pathology reports reference page — generates the diagnostic data that drives treatment decisions, including cancer staging and grading.

The U.S. Food and Drug Administration (FDA) regulates biopsy devices such as needles, forceps, and cutting instruments as Class II or Class III medical devices under 21 CFR Part 880, depending on their intended use and risk profile. Pathology laboratories processing biopsy specimens must comply with the Clinical Laboratory Improvement Amendments (CLIA), administered by the Centers for Medicare & Medicaid Services (CMS), which set proficiency, quality control, and personnel standards for laboratory testing (CMS CLIA program).

The scope of biopsy extends beyond cancer. It is used to diagnose infections, inflammatory conditions, and autoimmune diseases. In oncology, however, the biopsy occupies a central position — it is the required step between a suspicious finding on imaging or a flagged result on a blood test or tumor marker panel and a confirmed diagnosis.

How it works

Regardless of type, every biopsy follows a structured sequence:

Clinical indication and imaging review — The ordering physician identifies a lesion, mass, or abnormal region based on prior imaging, physical examination, or laboratory findings.
Method selection — The biopsy type is chosen based on lesion location, size, accessibility, and the amount of tissue required for analysis.
Patient preparation — Depending on the procedure, preparation ranges from topical anesthetic (for surface shave biopsies) to fasting and sedation (for endoscopic or surgical biopsies).
Specimen collection — Tissue or cells are removed using the selected instrument under image guidance, direct visualization, or palpation.
Specimen processing — The sample is fixed, sectioned, stained, and reviewed under light microscopy. Immunohistochemistry, molecular profiling, or cytogenetic analysis may follow, as outlined on the molecular profiling and biomarkers page.
Pathology report generation — The pathologist issues a formal report characterizing the specimen. Clinicians and patients may seek second opinions on cancer diagnosis when results are ambiguous.
Clinical integration — Results are incorporated into the diagnostic and treatment framework, which may include additional imaging for cancer or genetic testing for cancer risk.

The accuracy of a biopsy depends heavily on sampling adequacy. A core needle biopsy typically yields a cylinder of tissue 1–2 mm in diameter and 10–20 mm in length, which provides substantially more architectural information than a fine-needle aspirate, which collects only dispersed cells.

Common scenarios

Fine-needle aspiration (FNA): A 22–25 gauge needle aspirates cells from a palpable or image-visible mass. FNA is commonly used for thyroid nodules, enlarged lymph nodes, and superficial soft-tissue masses. It yields cytologic (cell-level) information but not tissue architecture, which limits its utility when architectural patterns are diagnostically important.

Core needle biopsy (CNB): A larger-gauge hollow needle removes a core of tissue. CNB is standard for breast masses, prostate evaluation (typically 12 systematic cores plus targeted cores under ultrasound guidance per established protocols), and liver or kidney lesions. Because it preserves tissue architecture, CNB supports histologic grading and receptor testing — critical inputs for breast cancer and prostate cancer treatment planning.

Stereotactic and image-guided biopsy: For lesions not palpable or not visible by ultrasound — such as microcalcifications found on mammography — stereotactic guidance uses two-dimensional X-ray images to calculate three-dimensional coordinates. MRI-guided biopsy is used for lesions visible only on MRI. CT-guided biopsy is employed for deep thoracic or abdominal lesions, including suspected lung cancer or pancreatic cancer nodules.

Endoscopic biopsy: Forceps passed through a bronchoscope, colonoscope, or endoscope sample mucosal tissue directly. This is the standard approach for colorectal cancer screening follow-up and evaluation of esophageal or gastric lesions. The American Cancer Society's cancer screening guidelines specify colonoscopy with biopsy capability as a preferred colorectal cancer screening method.

Excisional and incisional biopsy: Excisional biopsy removes the entire lesion; incisional biopsy removes only a portion. These surgical approaches are used when needle techniques are nondiagnostic or when the lesion is small enough that complete removal is both diagnostic and therapeutic — common in skin cancer evaluation.

Liquid biopsy: Rather than extracting solid tissue, a liquid biopsy analyzes circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), or other biomarkers from a blood draw. The FDA has authorized specific liquid biopsy assays as companion diagnostics; for example, the FoundationOne Liquid CDx received FDA approval for pan-tumor use in 2020 (FDA approval announcement). Liquid biopsy is not yet a replacement for tissue biopsy in most initial diagnoses but is established in monitoring treatment response and detecting resistance mutations.

Decision boundaries

Selecting a biopsy method involves four primary considerations:

Tissue quantity required: Molecular profiling, genomic sequencing, and biomarker analysis require more material than basic histology. When molecular profiling is anticipated, core needle or surgical biopsy is preferred over FNA.

Anatomical access and patient risk: Deep lesions near major vessels or within the brain carry higher procedural risk. In such cases, the risk-benefit calculation may favor liquid biopsy, a less invasive sampling route, or deferral pending additional imaging — a determination made within the broader regulatory context for oncology that governs clinical decision-making standards.

Prior results and diagnostic adequacy: A nondiagnostic biopsy — one yielding insufficient tissue or indeterminate pathology — does not confirm absence of malignancy. Rebiopsy rates for core needle biopsy of breast lesions are reported in the range of 5–15% in published prospective studies, depending on lesion type and operator experience.

Urgency and clinical trajectory: For presentations associated with unexplained weight loss, fatigue, or other warning signs, expedited biopsy pathways reduce time-to-diagnosis. Multidisciplinary tumor boards at NCI-designated cancer centers routinely review biopsy method selection as part of coordinated diagnostic planning, as documented in NCI's guidance on comprehensive cancer centers.

The oncology community's approach to cancer diagnosis and evaluation treats biopsy not as a single event but as the anchor of a diagnostic system that connects imaging, laboratory, genomic, and clinical findings into a coherent picture of disease.

References

The law belongs to the people. Georgia v. Public.Resource.Org, 590 U.S. (2020)