What investigations take place prior to surgery for Medullary Cancer?
Similar tests are performed as described for the surgery of a simple goitre. In addition to the standard tests, careful assessment of the adrenal glands for tumour activity is mandatory (24 hour urine collections and blood tests to exclude a phaeochromocytoma of the adrenal). Blood tests for calcium and parathyroid hormone levels will identify the presence or absence of parathyroid tumours. If the blood tests suggest parathyroid or adrenal tumours exist then special radioactive scans are used to pinpoint the tumours (these must not be used in pregnancy, however a MRI scan is safe).
What happens if Adrenal or Parathyroid tumours are discovered?
Tumours of the parathyroid can be dealt with when the total thyroidectomy is performed. Patients with phaeocromocytomas must be rendered safe by medication and adrenal tumours removed before total thyroidectomy is contemplated.
When should preventative (prophylactic) surgery be performed for Medullary Cancer?
Once it is known that a child has a germline mutation in the RET gene it is essential that the surgery takes place before there is tumour development. Invasive tumours have been described in children as young as 3 years old. It is considered foolhardy to delay surgery beyond three years of age. There is however recent evidence that molecular testing may detect subgroups of the mutation, which may allow surgery to be performed later than three years old.
What does the thyroid surgery entail for Medullary Thyroid Cancer?
The surgery is very similar to that for simple goitre. It is however more extensive; the thyroidectomy must be total (radioactive iodine is useless in this condition),all the lymph nodes and tissue in front of the windpipe must be removed including the thymus (this gland lies behind the breast bone)and be subjected to intra-operative frozen pathology.This practice is supported by a recent paper in 2008 from Europe that showed that if the lymph nodes in front of the windpipe(level 6) were not involved with cancer that the risk of lateral nodes(levels 2,3,4) being involved was only 10.1%.In contrast if one to three lymph nodes in level 6 are involved the risk of levels 2,3,4 involvement rises to 77%.With four or more positive level 6 lymph nodes level 2,3,4 involvement is 98%.This study has confirmed our view of an association between level 6 and levels 2,3 and 4 lymph node involvement.This means that the number of level 6 lymph nodes involved is a guide to the extent of level 2,3 and 4 lymph node dissection.If a single level6 lymph node is involved then an ipsilateral level 2,3,4 dissection is mandatory. Only if ten or more level 6 nodes are invoved is contralateral level 2,3,4 lymph node dissection considered necessary.We however have a lower threshold for contralateral level 2,3,4 dissection.If ideal surgery has not been performed at the first operation then a completion lymph node dissection must be considered.
Click here to review a short case study of sternal medullary thyroid metastases
It is important to remove the tumour, as left untreated the tumour can erode into the chest wall.
A tumour eroding into the chest wall - click to enlarge
During the operation lymph nodes in the side of the neck will be checked by the pathologist for cancer and if they are involved they are removed.
Neck dissection - click to enlarge
Lymph node metastasis - click to enlarge
The lymph nodes removed - click to enlarge
The parathyroids may be enlarged and one or more enlarged glands may need to be removed (this is not necessary in sporadic or MEN 2B because the parathyroids are normal in these patients.) If the tumour extends into the chest it may be necessary to divide the breastbone to remove the entire tumour.