The process involves the extraction of sample cells or tissues for examination to determine the presence or extent of a disease.

The tissue is then fixed, dehydrated, embedded, sectioned, stained and mounted[1] before it is generally examined under a microscope by a pathologist; it may also be analyzed chemically.

[2][3] The term biopsy reflects the Greek words βίος bios, "life," and ὄψις opsis, "a sight.

[citation needed] When intact removal is not indicated for a variety of reasons, a wedge of tissue may be taken in an incisional biopsy.

[6] Pathologic examination of a biopsy can determine whether a lesion is benign or malignant, and can help differentiate between different types of cancer.

Examination of the full mastectomy specimen would confirm the exact nature of the cancer (subclassification of tumor and histologic "grading") and reveal the extent of its spread (pathologic "staging").

[10] In addition, excisional biopsies are invasive, cannot be used repeatedly, and are ineffective in understanding the dynamics of tumor progression and metastasis.

[11][12] By detecting, quantifying and characterisation vital circulating tumor cells or genomic alterations in CTCs and cell-free DNA in blood, liquid biopsy can provide real-time information on the stage of tumor progression, treatment effectiveness, and cancer metastasis risk.

[13] This technological development could make it possible to diagnose and manage cancer from repeated blood tests rather than from a traditional biopsy.

[13][14][15][16] Circulating tumor cell tests are already available but not covered by insurance yet at maintrac and under development by many pharmaceutical companies.

Companies offering cfDNA next generation sequencing testing include Personal Genome Diagnostics and Guardant Health.

[23] Biopsy specimens are often taken from part of a lesion when the cause of a disease is uncertain or its extent or exact character is in doubt.