Thyroid surgery - introduction

This section contains information on the details of a thyroid operation, including what tests are done before surgery, the types of operation available and the details of operations. There are various sections written in detail for surgeons, which may contain pictures of surgery that some people may not wish to see.

In Mr Lynn's view there is no substitute for experience in thyroid surgery. Ideally the surgeon should perform at least 50 thyroidectomies a year. In 2007 the BAETS audit of thyroid surgery in the UK showed that 61% of its members reported performing less than 50 thyroidectomies a year (www.baes.info). Data from the USA has shown that low volumes of thyroid surgery are associated with a totally unacceptable complication rate compared to surgeons like Mr Lynn who performs more than 100 thyroidectomies a year. The BAETS feels that 25 thyroid operations a year is the lower threshold per year to maintain competency. If one considers that no more than 25% of patients will have cancer it means that operating on less than 10 thyroid cancer cases a year is considered satisfactory. This in my view is a very inappropriate view and is most likely the reason for the high complication rate quoted by some members of the BAETS.

Prior to most thyroid operations, apart from total thyroidectomy for Grave's Disease, a fine needle biopsy of thyroid should be performed (FNA).This procedure is relatively painless, can be performed with or without local anaesthesia, and ideally be performed under ultrasound control. A small needle (25-27 gauge) is inserted into the periphery of the nodule and the sample obtained by an up and down movement. As soon as blood appears the needle is rotated and removed.The patient is told not to swallow during the aspiration. The aspiration is done at least twice and ideally the pathologist should be present to check the adequacy of the specimen. If a cyst is aspirated it is important to biopsy the cyst wall. Only when the nodule is calcified or very fibrous is it necessary to use a Franzen's pistol (syringe holder). If a patient with a solitary thyroid nodule is not offered a FNA under ultrasound control they are advised to seek a second opinion.

The assessment of the results of fine needle aspiration is complex and the interpretation of the results is listed below. The classification is the THY diagnostic category system and ranges from THY1 which is non diagnostic, to THY5 which is diagnostic of thyroid malignancy. All results of FNA biopsy are discussed by Mr Lynn with his multidisciplinary team members (MDT).

#THY1

Non-diagnostic: should be repeated immediately (this occurs in 15-30% of cases and is more likely to occur if the nodule is less than 1 cm in diameter).

#THY2

Non-neoplastic (not malignant): As up to 10% can later be proven to be malignant, the FNA should be repeated in 3-6 months and if a similar result is obtained and the lesion is considered to be not clinically high risk It may be watched and not removed.In high risk cases thyroid lobectomy is justified. There is data that shows that once a lesion is classified as benign (THY2) on a single aspirate the risk of cancer is 10%. If a patient has 2 separate aspirates both benign (THY2) the risk of cancer falls to 1.2%. This is confirmed by data from Nottingham UK presented to the BAETS IN 2010. This report showed that a second aspiration converted a THY2 to THY3 status in 18.2% of cases but as expected only 1.3% were malignant. This data supports the British Thyroid Association recommending we do at least one more fine needle aspirations of the THY3 lesion.The approach to the THY2 lesion is slightly different in the USA. The American Thyroid Association recommends that a patient with THY2 lesion has a repeat ultrasound 6 to 18 months later and only if there is an increase in size of the nodule is a repeat ultrasound directed FNA performed. If there is no increase in size FNA is considered unnecessary and follow up is by ultrasound only if nodule is static.The advantage of the British approach is that once a second or third FNA is THY2 that long term follow up is unnecessary.The Oxford Group reported in 2010 to the BAETS the long term outcome of 2923 patients with a THY2 nodule diagnosis. The overall incidence of cancer in patients who later had surgery was 2.66 per 1000 per year. This seems alarming but the majority of the cancers were incidental and not clinically significant. This data means that it it is safe to treat THY2 lesions non surgically ,remembering to advise the patient that any change in status should be noted and indicate a review.

#THY3

Follicular lesion or suspected follicular cancer: these lesions should be removed and subjected to formal histology (5-30% are malignant). The percentage of THY3 lesions varies from center to center.The presentation in 2010 to the BAETS by groups from Dundee and Aberdeen has shown this. On rare occasions a lesion may be classified as THY3 because it is an inadequate specimen.In such cases it is perfectly correct to repeat the FNA and if the sample is adequate to re-classify it. If the lesion is malignant it should be treated as per the guidelines for the management of follicular thyroid cancer.

Mr Lynn has considerable concerns about the management of THY3 lesions. He thinks that the suggestion that thyroid ultrasound is more reliable in diagnosing cancer than FNA is wrong and dangerous. He has encountered radiologists, who despite the finding of THY3 cytology, tell the patient that the lesion is not malignant. Although the risk of malignancy can be low, it is impossible to exclude malignancy without removing the lesion by at least a thyroid lobectomy. Some groups classify the THY3 lesions into THY3A and THY3B subgroups . The malignancy rate is 28.2% in THY3A and 13% in THY3B . This confirms that failing to remove a thyroid lobe containing a THY3 lesion is foolhardy and downright dangerous. In the USA some physicians subject the patient to a radioactive scan. Their thinking is that if the THY 3 lesion is hot then it is unlikely to be malignant and as such does not need surgical removal. It is is indeed true that a THY3 that is hot is less likely than a cold lesion to be cancerous but cancer can occur in hot lesions. There are some anecdotal suggestions that when cancer occurs in a hot thyrotoxic THY3 lesion the disease tends to be very aggressive. In the UK a radioactive scan is not used and the THY3 patient is directly operated on.

#THY4

Suspicious of cancer and proven in 75% to 90%. If THY4 has been given due to a lack of material available to exclude medullary thyroid cancer or lymphoma then the FNA must be repeated and tissue subjected as appropriate to either immunocytochemistry (medullary thyroid cancer) or flow cytometry (lymphoma). In all other cases a THY4 report indicates the need for an immediate thyroid exploration, the extent of which is discussed by Mr Lynn with his MDT members since either lobectomy or total thyroidectomy may be initially appropriate.However a recent  presentation in 2010 to the BAETS of a 5 year experience of Thy 4 lesions from the ENT unit at Guy's and St Thomas' Hospital London demonstrated  a positive malignancy rate of 90%. This means that a single stage total thyroidectomy with level 6 lymph node clearance is in most cases the treatment of choice.

#THY5

97-99% diagnostic of thyroid cancer: the patient must have surgery, the extent of surgery depends on the type of tumour,its size and the tumour staging. A plan is discussed by Mr Lynn with his MDT members.

Recently Dr Paul Lewis our thyroid pathologist has introduced a THY"0" category in his reports. THY"0" is not cancerous and is defined as a fluid aspirate that contains no follicular epithelial cells but abundant macrophages. The THY"0"lesion is only resected if it is causing symptoms. One expects the concept of the THY"O" lesion to be widely used in the near future.

The UK Endocrine Pathology Society has excellent videos on how to do a FNA these can be seen on the website www.ukeps.com

In 2003 EUROCARE reported the UK survival for thyroid cancer as the worst in Europe. There were several factors affecting the reported results including accurate registration and UK regional variation. Few if any thyroid cancers are treated now without MDT input and when this occurs short term 5 year survival for thyroid cancer has has improved considerably and has been reported in a UK regional center as 83% (Gill et al Clinical Oncology, Sept 2008: 20:7,568).