A biopsy is a procedure that removes a small sample of cells or tissue from the body for examination under a microscope. It is the only definitive way to diagnose cancer and determine the type of cancer. However, there are some cases where a biopsy may not be needed to make a cancer diagnosis.
When is a biopsy needed to diagnose cancer?
In most cases, a biopsy is required to definitively diagnose cancer. Some examples of when a biopsy is typically needed include:
- If imaging tests like an MRI, CT scan, or ultrasound detect a suspicious mass or lesion
- If a screening test like a mammogram detects an abnormality
- If a blood test shows abnormalities that may indicate cancer
- If a doctor notices any signs or symptoms of cancer during a physical exam
A biopsy allows the pathologist to examine the cells or tissue under a microscope. Based on the appearance and characteristics of the cells, the pathologist can determine if they are benign or cancerous. The biopsy also allows the cancer to be classified by type based on the origin of the cells.
When may a biopsy not be required for a cancer diagnosis?
There are some situations in which a doctor may diagnose cancer without a biopsy, although this is less common. Cases where a biopsy may not be needed include:
- If imaging tests detect a tumor that is unmistakably cancerous. For example, multiple myeloma detected on an X-ray or PET scan.
- If the cancer is widely metastatic. A biopsy of a metastatic tumor may provide enough information for diagnosis.
- If the location of the tumor makes a biopsy risky. For example, a tumor near vital structures.
- If the patient is too ill to undergo biopsy. Their cancer diagnosis may be based on other test results.
However, even in the above situations, doctors will usually recommend a biopsy if it can be done safely. A tissue sample provides the most accurate diagnosis.
What are the risks of diagnosing cancer without a biopsy?
Relying on imaging tests or other non-biopsy methods to diagnose cancer has several risks, including:
- Incorrect diagnosis – Cancer may be mistaken for a benign condition, delaying treatment.
- Misclassification of cancer type – The origin and cell type of the cancer may be incorrectly categorized.
- Improper staging – Without examining tissue, it is difficult to determine how advanced the cancer is.
- Wrong treatment – Without an accurate diagnosis, the wrong treatment may be prescribed.
Studies show that in up to 25% of cases, cancers initially diagnosed by imaging alone turn out to be benign when a biopsy is done. Biopsies also identify cancers not seen on imaging in some cases.
What are the different types of biopsies used to diagnose cancer?
There are several biopsy procedures that may be used to extract cells or tissue to test for cancer:
- Needle biopsy – A hollow needle is inserted into the tumor to extract sample cells or fluid.
- Incisional biopsy – A small portion of the suspicious area is surgically removed for examination.
- Excisional biopsy – The entire abnormal growth is surgically removed.
- Endoscopic biopsy – Instruments are inserted into the body and directed to the tumor site to obtain a sample.
- Bone marrow biopsy – A sample of bone marrow is taken, usually from the hip.
The type of biopsy selected depends on the location of the abnormal cells and which method can safely obtain diagnostic material. Needle biopsies, like fine needle aspiration, are minimally invasive and often used as an initial procedure.
Fine needle aspiration (FNA)
FNA uses a very thin needle to extract fluid and cells from lumps or masses. It can be done rapidly in a doctor’s office. FNA is safe, simple, and cost-effective. It does not require surgery or hospitalization. The sample is inspected under a microscope for cancer cells.
Core needle biopsy
This obtains a small cylinder of tissue using a hollow needle. Several samples may be taken. It provides more tissue than FNA for diagnosis but is slightly more invasive.
Vacuum-assisted biopsy
This type of core needle biopsy uses vacuum pressure to pull tissue into the needle. It collects larger, more intact samples.
Incisional and excisional biopsy
These surgical biopsies require a cut into the skin and removal of tissue. They provide the largest samples but have longer recovery times and higher complication risks.
What are the possible complications from a biopsy?
Biopsies are generally safe procedures but do carry some risks, such as:
- Bleeding, especially if a blood vessel is damaged
- Infection at the biopsy site
- Pain, which may be mild to moderate
- Nerve damage if a nerve is cut during the procedure
- Leaking of biopsy fluid into surrounding tissues
- Scarring at the biopsy site
Serious complications after biopsy are uncommon. The risks are higher with surgical biopsies compared to needle biopsies. Talk to your doctor about the specific risks based on the type of biopsy you will have.
How should one prepare for a biopsy?
Preparation for a biopsy usually involves:
- Not eating or drinking for a certain time period before the biopsy based on instructions
- Arranging for someone to drive you home after the procedure
- Taking medications as prescribed by the doctor, which may include antibiotics or blood thinners
- Follow all pre-procedure directions provided
- Tell the doctor about any medications, supplements, or allergies
For incisional or excisional biopsies, additional steps may need to be taken, like blood work tests, an IV line insertion, and not taking blood thinners before surgery.
What happens during the biopsy?
The steps during a biopsy procedure include:
- The site is cleaned and a local anesthetic is applied to numb the area.
- The needle or biopsy instrument is inserted into the tumor or abnormal tissue.
- Cells or tissue samples are removed. Several samples may be taken.
- Pressure is applied after the biopsy to stop any bleeding.
- The tissue is sent to a lab for analysis by a pathologist.
- For surgical biopsies, the steps involve making an incision, removing tissue, and stitching the skin closed.
Imaging techniques like ultrasound, MRI, or CT scans may be used to guide the doctor when taking samples from deeper inside the body.
What happens after a biopsy?
After a biopsy, you can expect:
- Bandaging and covering of the biopsy site
- Instructions on caring for the biopsy site and watching for signs of infection
- Guidelines on physical activity restrictions for a certain time period
- Prescriptions for antibiotics or pain medications
- A follow-up appointment to get the biopsy results in 1-2 weeks
It is important to avoid strenuous activities for a few days after the biopsy and keep the site clean and dry.
How are biopsy samples analyzed?
The tissue samples are sent to a pathology lab to be analyzed under a microscope by a pathologist. The pathologist looks at the appearance and characteristics of the cells to determine if they are cancerous. Features that indicate cancer include:
- Irregular cell shapes and sizes
- Abnormal growth patterns
- Increased number of cell divisions
- Invasive behavior into surrounding tissue
If cancer is found, immunohistochemistry tests may further classify the type based on specific proteins on and within the cancer cells.
Molecular testing like DNA profiling helps identify genetic mutations that can inform treatment options. Testing for biomarkers can also help guide targeted therapies.
How accurate are biopsy results?
Biopsy accuracy depends on:
- Location – Harder to reach tumors may yield non-diagnostic samples.
- Sampling technique – More samples reduce the risk of a false negative.
- Pathologist expertise – An experienced pathologist leads to higher accuracy.
- Sample preservation – Proper handling maintains integrity for analysis.
For palpable masses, biopsies have an overall accuracy of over 95% when an adequate sample is obtained and analyzed by an expert pathologist. However, accuracy rates are lower for biopsies of tumors in harder to access locations.
What are the potential errors in biopsy results?
Some potential errors that can occur with biopsies include:
- Non-diagnostic or inadequate sample – No diagnosis can be made due to insufficient material for analysis.
- Sampling error – The biopsy misses the tumor and yields only normal tissue.
- Incorrect diagnosis – Benign conditions are mistaken for cancers and vice versa.
- Misclassification – Cancers arising from one organ are thought to originate elsewhere.
To reduce errors, it is important the biopsy sample tumor tissue rather than surrounding normal tissue. Taking multiple samples lowers the chances of sampling error.
How are cancer stages determined by biopsy?
The stage of cancer depends on factors like size, location, and spread. While biopsies cannot directly determine stage, examination of the cells can provide information to help determine stage, such as:
- Depth of invasion into surrounding healthy tissues
- Degree of differentiation and aggressiveness
- Vascular or lymphatic invasion
- Presence of premalignant changes
- Biomarkers associated with advanced stage cancers
imaging and other tests are also used along with biopsy results to fully stage the cancer.
What are the alternatives to a biopsy?
There are currently no alternatives that can definitively diagnose cancer without taking a sample of the tumor itself. Some newer technologies aim to become alternatives to surgical biopsy but require more research:
- Liquid biopsy – Detects tumor DNA in the blood from cancer cells shedding into circulation. Primarily used to monitor, not diagnose.
- Lab-on-a-chip – Microfluidic chip analysis of exfoliated tumor cells from body fluids like sputum or urine.
- Spectroscopy – Uses light scattering and absorption spectra to chemically analyze tissues.
- Optical coherence tomography – Provides real-time imaging of tissue microstructures.
While these show promise for non-invasive cancer testing, biopsy remains the gold standard diagnostic method.
Can a biopsy cause cancer cells to spread?
This is a common concern, but there is no good evidence that a biopsy can cause significant spread of cancer cells. Some important points:
- Only a tiny fraction of the tumor is extracted – More than 99% remains in the body.
- Dislodged cells do not easily survive or proliferate.
- The use of imaging can guide the needle away from blood vessels.
- Any disturbed cells would likely have entered circulation even without the biopsy.
Overall, the risk is very low except potentially in cases like lymphoma where the tumor is more diffuse. The benefit of an accurate diagnosis is considered to outweigh any minimal risks.
Can biopsy results be wrong?
Biopsy results can rarely be wrong. Some potential reasons include:
- The samples did not contain any tumor cells, leading to a false negative.
- Changes happen to the tumor between biopsy and treatment.
- Errors were made in tissue handling or pathology analysis.
- There is miscommunication of results between doctors.
- Biopsy site is incorrectly marked prior to excision.
Having a dedicated expert pathologist analyze the samples helps minimize the chances of incorrect biopsy results. But it is still possible for specimens to get switched or results misinterpreted in rare cases.
Getting a second opinion
If biopsy results are unexpected or conflicting with other tests, getting a second opinion from another pathologist can provide more confidence. A repeat biopsy may even be warranted, especially if the initial one was nondiagnostic.
Conclusion
While a tissue biopsy remains the gold standard for definitively diagnosing most cancers, there are some exceptions where imaging and blood markers may be enough to make a diagnosis without an invasive procedure. However, the risks of misdiagnosis usually make biopsy recommended. The range of biopsy techniques allows sampling of most tumor sites with minimal side effects. When properly handled and analyzed, biopsy results accurately identify cancerous tissues in over 95% of cases.