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Why is a biopsy important for diagnosing cancer?

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Precancerous growth in a human colon — cancer View through an endoscope of a polyp, a benign precancerous growth projecting from the inner lining of the colon.

Biopsies are considered the most definitive diagnostic tests for cancer. They are essential because they allow pathologists to examine cells or tissues under a microscope to render a precise diagnosis, distinguishing between malignant and benign tumors.12

By collecting tissue samples—whether through excisional biopsy, incisional biopsy, or needle biopsy—physicians can analyze cellular and architectural characteristics. This process is often supplemented by advanced methods, including:12

Microscopic Examination: Viewing stained tissue sections to define cellular features.12
Specialized Analysis: Using electron microscopy or immunohistochemical staining with antibodies to identify specific proteins.1
Molecular Testing: Employing biological techniques to detect mutations in oncogenes or analyzing chromosome content.1

During surgery, "frozen sections" provide rapid results with high diagnostic accuracy, helping surgeons confirm if a tumor has been completely removed. Ultimately, the biopsy provides the critical evidence needed to guide clinical decisions and treatment strategies.12