Sentinel lymph node biopsy

Overview

A sentinel lymph node biopsy is a surgical procedure used to check whether cancer has spread to the lymph nodes, the small glands that help filter fluids and fight infection. It is most often done for breast cancer or melanoma (a type of skin cancer). The sentinel node is the first lymph node that cancer cells would likely reach after leaving the original tumour. By removing and testing this node, doctors can see if the cancer has started to spread without removing many nodes.

Sentinel lymph node biopsy is a standard procedure for many people with breast cancer or melanoma. It is not rare, but not every person with cancer needs it — your doctor will decide based on your specific situation.

It is mainly used for people diagnosed with certain types of cancer, especially breast cancer and melanoma. It may also be used for some other cancers, such as vulval or penile cancer, but this is less common.

Symptoms

Common symptoms

• Sentinel lymph node biopsy itself does not cause symptoms — it is a test. However, you may have a small lump or swelling in the armpit or groin if a lymph node is enlarged due to cancer.

Symptoms in children

• Sentinel lymph node biopsy is very rarely done in children. If it is needed, the same principles apply, but the child's size and development are taken into account.

Symptoms in older adults

• Older adults may have a higher risk of complications from the injection of blue dye or tracer, but the procedure is generally safe. They may also have a slower recovery from the small incision.

Causes

Main causes

• A diagnosis of cancer that can spread through the lymphatic system, such as breast cancer or melanoma, is the reason a sentinel lymph node biopsy may be recommended.

Risk factors

• Having a cancer that is known to spread to lymph nodes.
• The cancer being larger or more aggressive increases the chance that the sentinel node might contain cancer cells.

When to see a doctor

See a doctor urgently if:

• Any signs of allergic reaction during the tracer injection (hives, difficulty breathing, swelling of lips or tongue) — seek emergency care immediately.
• After the procedure: heavy bleeding from the biopsy site that does not stop with pressure.

Book a routine appointment if:

• If you have been diagnosed with cancer and you have not yet discussed sentinel lymph node biopsy with your surgeon.
• If you notice a new lump in your armpit or groin before or after a cancer diagnosis.

Diagnosis

Sentinel lymph node biopsy is not used to diagnose cancer — it is done after cancer has been found to see if it has spread. The procedure is usually part of the treatment plan.

Tests that may be done

• A lymphoscintigram — a scan done before or during surgery to find the sentinel node using a small amount of radioactive tracer.
• Injection of a blue dye near the tumour during surgery to make the sentinel node visible.
• A hand-held gamma probe (a device that detects radiation) to help the surgeon find the node.

What to expect at your appointment

You will have a small cut (incision), usually in your armpit or groin. The surgeon will find the sentinel node using the tracer and dye, remove it, and send it to a lab. You will be under general anaesthesia or local anaesthesia with sedation. The procedure takes about an hour. You may have some bruising or a temporary blue discolouration of your urine and skin from the dye, which fades within a day or two.

Treatment

Sentinel lymph node biopsy itself is a diagnostic procedure, not a treatment. However, the result helps guide further treatment. If the sentinel node contains cancer cells, additional treatment may be needed — such as removing more lymph nodes, or using radiotherapy or medication (chemotherapy or targeted therapy). Your doctor will explain what the findings mean for you.

Self-care at home

• Keep the biopsy site clean and dry for at least 24 hours (follow your doctor's instructions).
• Apply a cold pack (wrapped in a cloth) to reduce swelling if needed.
• Avoid heavy lifting or strenuous activity with the affected arm for a few days.
• Watch for signs of infection (redness, pain, discharge) and contact your healthcare team if they occur.

Medical treatments

If the sentinel node is positive (contains cancer), your cancer team may recommend further surgery to remove additional lymph nodes (lymph node dissection). They may also suggest post-operative treatments such as radiotherapy, chemotherapy, hormone therapy, or targeted therapy — depending on the type and stage of cancer. Always discuss all options with your specialist.

When is surgery considered?

Sentinel lymph node biopsy is a surgical procedure. It is usually done at the same time as your main cancer surgery (for example, lumpectomy or mastectomy). In some cases, it is done as a separate, shorter operation.

Living with this condition

Most people recover quickly from sentinel lymph node biopsy. You can usually return to normal activities within a few days. However, you may have some numbness or tingling near the incision for a few weeks. If you had a lymph node dissection later, you may need to take precautions to prevent arm swelling, such as avoiding blood draws or injections in that arm.

Lifestyle tips

• Be mindful of any changes in your arm or leg near the biopsy site — if swelling occurs, speak to your doctor about managing it.
• Keep your skin healthy and avoid cuts or scratches on the affected side to reduce infection risk.
• Do gentle arm exercises as recommended by your physiotherapist or cancer nurse.

Diet and exercise

A balanced diet rich in fruits, vegetables, and lean protein can support healing. Moderate exercise, such as walking, is fine after the first day or two. Avoid heavy lifting or vigorous activity until your doctor says it is safe.

Mental health and emotional wellbeing

Waiting for biopsy results can be stressful. It is normal to feel anxious or worried. Talk to your healthcare team about your feelings. They can connect you with a counsellor or support group. If you feel overwhelmed, reach out to a mental health professional or a crisis helpline.

Prevention

Sentinel lymph node biopsy is a test, not a disease, so there is nothing to prevent. However, early detection and treatment of cancer may help reduce the chance of needing extensive lymph node surgery.

Complications

If left untreated

• If the sentinel node is found to contain cancer and no further action is taken, the cancer could continue to spread to other lymph nodes and beyond, potentially making treatment more difficult.
• After the biopsy, if you ignore signs of infection (like redness or pus), the infection could worsen and require antibiotics or further medical care.

Long-term outlook

For most people, sentinel lymph node biopsy is a safe, low-risk procedure that gives important information to guide cancer treatment. When cancer is found in the sentinel node, early treatment can still be very effective. Thanks to modern treatments, many people with positive nodes go on to live full, healthy lives. Your healthcare team will tailor a plan just for you.

Find support

External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.