Block Dissection – Axilla (armpit), Groin or Neck

Patient Experience

  • Reference Number: HEY-260/2023
  • Departments: Plastic Surgery
  • Last Updated: 30 June 2023


This leaflet has been produced to give you general information about your forthcoming surgery.  Most of your questions should have been answered by this leaflet.  It is not intended to replace the discussion between you and your doctor, but may act as a starting point for discussion.   If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team.

What is a block dissection?

Block dissection surgery involves surgically removing most of the lymph nodes (glands) from a specific part of the body.  Surgery can be performed on the neck, armpit or groin.

Lymph nodes are part of the lymphatic system. The lymphatic system is made up of vessels (similar to blood vessels) that drain away excess fluid from the body. Fluid drains from these vessels into lymph nodes.  Large collections of these lymph nodes can be found in your armpits, groins, and the neck area. Lymph nodes are part of the immune system to fight infection, but also filter cancer cells.

Why do I need block dissection surgery?

Various tests that the doctors may have performed (such as CT scans, fine needle biopsy, sentinel node biopsy surgery) have shown that cancer cells could potentially be present in the lymph nodes in your groin, armpit or neck. The doctor will inform you which part of the body will be operated on.

Please note that block dissection surgery and completion lymphadenectomy are the same procedure.

Possible advantages of completion lymphadenectomy Possible disadvantages of completion lymphadenectomy
Removing the rest of the lymph nodes before cancer develops in them reduces the chance of the cancer returning in the same part of the body. Lymphedema (long-term swelling) may develop, and is most likely if the operation is in the groin and least likely in the head and neck.
The operation is less complicated and safer than waiting until cancer develops in the remaining lymph nodes and then removing them. In 4 out of 5 people, cancer will not develop in the remaining lymph nodes, so there is a chance that the operation will have been done unnecessarily.
People who have had the operation may be able to take part in clinical trials of new treatments to prevent future melanoma. These trials often cannot accept people who have not had this operation. There is no evidence that people who have this operation live longer than people who do not have it.
Having any operation can cause complications.
If you have had surgery due to the recurrence of your melanoma and there is no suggestion of disease elsewhere you could be eligible for adjuvant treatments for a year to reduce the risk of the cancer recurring after surgery. Adjuvant treatment can be given either intravenously (a needle in the arm) every 4-6 weeks for immunotherapy or by taking tablets orally for targeted treatments. The type of treatment is dependent on the type of melanoma you have. Please note adjuvant treatments are not suitable for all patients and they do have side effects.

What does the surgery involve?

The surgery is performed under a general anaesthetic (while you are asleep). There are potentially 20-30 nodes in each armpit, groin or side of neck. The surgeon removes as many nodes as they can without causing problems to surrounding blood vessels and nerves. The scars from the operation depend on which area is operated on:

  • For the neck, the scar runs down behind your ear toward the jaw, then down the neck in a straight line.
  • For the armpit, the scar runs from under your armpit down the inside of your arm.
  • For the groin the scar runs from the natural fold in your groin down the front of your leg.

After the surgery

When you wake up from the operation you will have a cannula (plastic needle) in your hand, which will have fluid administered into it (intravenous fluids). This will remain in place until you are eating and drinking sufficiently.

Blood can sometimes collect under the wound (known as a haematoma). To try and prevent this from happening, a bottle (suction) drain will be put into the area during the surgery. This allows blood to be collected into a bottle and not cause problems under the wound. This drain will stay in place until the drainage settles down. The drain may need to stay in for several days, and you may find that the fluid collected will turn from blood to a yellow coloured fluid. This is lymph fluid which is normal. This bottle drain will not stop you walking about after the operation.

If you have had surgery on your groin you may wake up from the operation with a catheter in place (this is a tube that goes into your bladder, so when you need to pass urine it is collected in a bag). The catheter will remain in place until you are more mobile.

The operation can be uncomfortable requiring you to need analgesia (pain relief). The nurses on the ward will ask you frequently if the pain relief is working, if it is not, please let them know. You do not need to be in any pain.

After the surgery you may find you do not feel like getting up out of bed until the next day. The nurses will help you getting out of bed and encourage you to gently mobilise.

Can there be any complications or risks?

Because the procedure is performed under a general anaesthetic there is the risk of deep vein thrombosis (DVT) and pulmonary embolism (a clot in the lungs). These risks may be reduced by the aid of an injection that you will receive daily which thins your blood, thus preventing clots. It can cause you to bruise easily. You will also be asked to wear white stockings which help pump the blood through your legs.

The risk of developing a chest infection after surgery is greatly increased if you are a smoker.

Because you are having an incision (cut in the skin) made, there are the risks of developing an infection, wound breakdown, bruising and permanent scarring.

During the operation you may lose some blood, but it is very rare to require a blood transfusion.

Numbness around the scar is common after this surgery and is usually permanent. If the surgery is performed on the neck area there is a risk of temporary paralysis of the side of the face where surgery was performed. This is very rarely permanent.

Because the lymph nodes drain fluid, once these nodes have been removed you can get a seroma (fluid) collecting under the scar. This is a common complication that usually occurs after you are discharged from the hospital. The fluid is removed by inserting a needle into the area and being drained off. This procedure is usually performed in the Outpatients department and may need to be done several times until it resolves on its own.

Far less common is the development of lymphoedema which is swelling (oedema) of a limb caused by the build up of lymph fluid, which normally flows through lymph glands. After this operation the body finds a way to redirect this fluid, but in a small number of cases people can develop lymphoedema. It cannot be cured, but if caught early enough the effect of lymphoedema can be minimised. During your post-surgery, follow up appointments a nurse will discuss with you about the potential development of lymphoedema and provide you with written information.

How do I prepare for the operation?

Please read the information leaflet.  Share the information it contains with your partner and family (if you wish) so that they can be of help and support.  There may be information they need to know, especially if they are taking care of you following this operation. 

Please take your medication as normal unless given other information by the pre-admission nurses. The pre-admission nurses will also inform when you should stop eating and drinking before your operation and what medication you can take.

If you have further question about your admission to hospital, please contact your Clinical Nurse Specialist (01482) 461078 

Going home

Once you have been discharged please ensure that all dressings are kept clean and dry. Ensure that you have adequate pain relief at home.

If you go home with your drain insitu, you will be given information from the ward on how to manage this at home. Any problems please phone the Plastic Surgery nurses helpline on 01482 623259 (Monday-Friday) for weekends/Bank holidays please phone the Plastic Surgery Trauma clinic on 01482 764509.

You should avoid any strenuous activities, exercise or heavy lifting (this includes children) for about 4-6 weeks following your operation. You should not drive until after your outpatient appointment; your doctor or nurse will advise you further. You will be given more information on this when you are discharged from the ward.  If you require a Statement of Fitness for Work (formerly a sick certificate) before you are discharged, this can also be arranged.

What happens afterwards?

You will usually be given an outpatient appointment for your wounds to be checked about 7-14 days after surgery. At this appointment, all dressings and stitches will be removed as required.  All the nodes that were removed at the time of surgery are sent away to a laboratory and analysed under a microscope to see if any cancer cells are present (histology). If the results are available, you will be informed of them at this clinic appointment. If they are not, you will be sent an appointment once they have been received or your clinical nurse specialist nurse team will be in contact. Please note results can take between 4-6 weeks.

You will be followed up at the hospital for some years, even if the histology is clear. If the histology shows that cancer cells were present in the lymph nodes, there is the possibility that further treatment may be required. This would not normally involve more surgery but could potentially involve chemotherapy, radiotherapy or immunotherapy.  Your doctor or nurse will explain these treatments with you if they are felt necessary.

Should you require further advice on the issues contained in this leaflet, please do not hesitate your Clinical Nurse Specialist (01482) 461078

This leaflet was produced by the Plastic Surgery Department, Hull University Teaching Hospitals NHS Trust and will be reviewed in June 2026.

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

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We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

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