Radiation exposure (papillary).Populations with low dietary iodine have a higher proportion of follicular and anaplastic cancers.
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In differentiated thyroid carcinoma, several classification and In differentiated thyroid carcinoma, several classification and staging systems have been introduced. However, no clear staging systems have been introduced. However, no clear consensus has emerged favoring any one method over another consensus has emerged favoring any one method over another
Embryology• 4th week: thyroid gland appears.• 5th week: break down of the thyroglossal duct, thyroid gland continue descending• 7th week: thyroid gland migrates to its position, anterior to the trachea• 10th week: thyroglossal duct disappears<br />
Anatomy<br />Locate deep to the sternohyoid muscle, <br />from level C5 to T1 vertebrae or anterior to the 2nd and 3rd tracheal rings.<br />Thyroid gland is attached to the trachea by the lateral suspensory (Berry) ligaments.<br />
Blood supply<br />Blood supply: sup. & inf. thyroid arteries<br />thyroid ima artery (1.5% to 12%)<br />
<ul><li>Lymph vessels: </li></ul>drain to <br /><ul><li>prelaryngeal,
Thyroid physiology<br /><ul><li>5 steps of thyroid hormone formation</li></ul>Iodide absorption in gut<br />Peroxidation of iodide<br />Binding with tyrosine<br />Formation of MIT & DIT<br />Coupling and formation of T3 & T4<br /><ul><li>Negative feed back mechanism</li></li></ul><li>Frequency<br />17,000 cases diagnosed annually.<br />Women 3 times more than men.<br />Peak incidence 30-40s.<br />Papillary 80%, follicular 10%, medullary 5-10%, anaplastic 1-2%.<br />
STAGING FOR DIFFERENTIATED STAGING FOR DIFFERENTIATED THYROID CANCER THYROID CANCER<br />TNM system<br />AMES system<br />AGES System<br />GAMES system<br />MACIS system<br />University of Chicago system<br />Ohio State University system<br />National Thyroid Cancer Treatment Cooperative Study (NTCTCS)<br />
TNM Classification<br />Tx- size of primary tumor unknown<br />T1- tumor size < 2 cm<br />T2- tumor size 2-4 cm<br />T3- tumor size >4 cm with minimal extra-thyroidal extension<br />T4a- tumor of any size with extra-thyroidal involvement up to trachea, esophagus, larynx, RLN<br />T4b- tumor invades paravertebral fascia, carotid artery, mediastinal lymph nodes<br />
Nx- nodes not assesed<br />N0- no nodes involved<br />N1- node involvement up to level 1(pretracheal. Paratracheal, prelaryngeal)<br />N2- cervical or superior mediastinal l/node involvement<br />
Mx- extent of mets can not be assesed<br />M0- no metastases<br />M1- presence of distant mets<br />
University of Chicago system<br />An easy An easy- to-remember staging system for papillary carcinoma <br />Class I— disease limited to the thyroid gland<br />Class II— lymph node involvement<br />Class III— extrathyroidal invasion<br />Class IV — distant metastases<br />
National Thyroid Cancer Treatment Cooperative Study (NTCTCS)<br />The NTCTCS created a staging approach that was<br />applied prospectively to a registry of patients drawn<br />from 14 cooperating institutions . pathologic <br />staging was based upon:<br /> patient age at diagnosis<br /> tumor histology<br /> tumor size<br /> intrathyroidalmultifocality<br /> extraglandular invasion<br /> metastases<br /> tumor differentiation<br />
MAICS Scoring MAICS Scoring<br /> Developed by the Mayo Clinic for staging<br /> It is known to be the most accurate predictor of a patient's outcome patient's outcome with papillary thyroid cancer<br />(M = Metastasis, A = Age, I = Invasion, C = Completeness of (M = Metastasis, A = Age, I = Invasion, C = Completeness of <br />Resection, S = Size) Resection, S = Size)<br />MAICS Score MAICS Score 20 year Survival 20 year Survival<br /><6 <6 = = 99% 99%<br />6 6- -7 7 = = 89% 89% <br />7 7- -8 8 = = 56% 56% <br />>8 >8 = = 24% 24%P<br />
Papillary Carcinoma<br />Most common (80%)<br />Women 3 times more common<br />30-40 years of age<br />Familial also<br />Radiation exposure as a child<br />Patients with Hashimoto’s thyroiditis<br />Slow growing, TSH sensitive, take up iodine, TSH stimulation produces thryroglobulin response.<br />
Papillary Carcinoma<br />Pathology:Unencapsulated, arborizing papillae. Well differentiated, rare mitoses.<br />50% have psammoma bodies (calcific concretions, circular laminations.<br />Multicentric with tumor present in contralateral lobe as well.<br />
Papillary Carcinoma<br />Local invasion through capsule, invading trachea, nerve, causing dyspnea, hoarseness.<br />Propensity to spread to the cervical lymph nodes. Clinically evident in 1/3 patients. Most commonly central compartment, located medial to carotids, from hyoid to sternal notch.<br />Distant spread to bone, lungs.<br />
Follicular Carcinoma<br />Second most common (10%)<br />Iodine deficient areas<br />3 times more in women<br />Present more advanced in stage than papillary<br />Late 40’s<br />Also TSH sensitive, takes up iodine, produces thryroglobulin.<br />
Follicular Carcinoma<br />Pathology: round, encapsulated, cystic changes, fibrosis, hemorrhages. Microscopically, neoplastic follicular cells.<br />Differentiated from follicular adenomas by the presence of capsule invasion, vascular invasion.<br />Cannot reliably diagnose basedon FNA.<br />
Follicular Carcinoma<br />Local invasion is similar to papillary cancer with the same presentation.<br />Cervical metastases are uncommon.<br />Distant metastases is significantly higher (20%), with lung and bone most common sites.<br />
Treatment and Prognosis<br />Controversy regarding extent of therapy continues.<br />Surgical excision whenever possible.<br />Total thyroidectomy has been mainstay (all apparent thyroid tissue removed). Complications include nerve damage bilaterally, parathyroid injury bilaterally.<br />After, get radioiodine scan, ablation if residual disease or recurrence.<br />
Treatment and Prognosis<br />Over the years, modification to procedure to reduce the above complications.<br />Subtotal thyroidectomy( small portion of thyroid tissue opposite the side of malignancy is left in place) and postop ablation.<br />Thyroid lobectomy and isthmectomy also a viable option with small tumors<br />
Neck<br />Examine the neck prior to surgery to detect lymph node spread.<br />Gross cervical mets should be removed en bloc with a dissection in the compartment in which they reside.<br />Excision of single nodes is not adequate.<br />Elective lymph node dissection is not done, as radioactive iodine takes care of this.<br />
Postoperative Radioiodine and Ablation<br />Radioiodine targets residual thyroid tissue and tumor after thyroidectomy.<br />Given in diagnostic doses and therapeutic doses to ablate tissue.<br />
Thyroid Suppression Therapy<br />Maintained on thyroxine after surgery and ablation. Low TSH levels reduce tumor growth rates and reduce recurrence rates.<br />Most recommend TSH levels of 0.1 mU/l.<br />Follow-up q 6 months with thyroglobulin levels and repeat scans.<br />Thyroglobulin is good because well differentiated tumors produce it.<br />
Prognosis<br /><ul><li>Age: at diagnosis. Cancer relate death more common if patient is older than 40 years.
Recurrences common in patients diagnosed when they were less than 20 years or olderthan 60 years.
Tumors greater than 4 cm have higher recurrence, death.</li></li></ul><li>Prognosis<br /><ul><li>Histology:papillary has 30 year cancer related death rate of 6%. Follicular has a 30 year cancer related death rate of 15%.
Distant metastases associated with a 68.1-fold increase in the rate of disease specific death.</li></li></ul><li>Hurthle Cell<br /><ul><li>A variant of follicular, also known as oncocytic carcinoma. 5 year survival 50%.
More common in women than men, presents in 5th decade of life.
Does not take up iodine, so treat aggressively.
Thyroid suppression and radioiodine don’t work.</li></li></ul><li>Medullary Carcinoma<br />5%, female preponderance<br />75% sporadically, 25% familial. Familial cases are usually all over the gland, sporadic usually not multifocal.<br />MEN 2A, MEN2B and FMTC syndromes.<br />
Men 2a, 2b, FMTC<br /><ul><li>MEN 2a is Sipple syndrome,MTC, pheochromocytoma, hyperparathyroidism.
MEN 2b is MTC, pheo, ganglionomas, marfan habitus.
Medullary cancer in these are most aggressive, younger age, rapid growth and metastases.
In sporadic you get painless nodule, symptoms of invasion.</li></li></ul><li>Biochemical Testing<br />Stimulating calcitonin release with IV pentagastrin increases sensitivity of test.<br />First measure baseline calcitonin, then give pentagastrin. Measure calcitonin serially 1.5 and 5 min later.<br />Used as tumor marker postop rather than screening now.<br />Use genetic testing for screening.<br />Histologically test for calcitonin and CEA.<br />
Treatment<br />Total thyroidectomy<br />Lymph node dissection of level VI.<br />Parathyroid reimplantation if necessary.<br />Lymph node mets are very common.<br />Prophylactic thyroidectomy in children with MEN 2a,b.<br />Surveillance with CEA, calcitonin.<br />Does not take up iodine, so no radioiodine.<br />Prognosis 10 y is 65%.<br />