Thyroid gland

Anatomy

Bi-lobed gland over second and third tracheal ring

piramidal lobe : 40 – 50 % Weight : 20 – 30 gr Epithelium lined follicle Colloid : glycoprotein ( thyroglobulin ) Vascular stroma True connective tissue capsule

It is important to ligate the superior thyroid artery close to the gland to avoid injury to the nerve during thyroidectomy

Inferior thyroid artery

Inferior thyroid artery :

Thyrocervical trunk

Absent in up to 6% Thyroidea ima :

directly from aorta , innominate artery or right common carotid artery

Present in up to 12%

Superior thyroid vein : IJV or common facial vein

Inferior jugular vein : innominate vein or IJV Middle thyroid vein : IJV Lymphatic → paratracheal nodes → superior

mediastinum & middle deep cervical node and lateral the neck

Embryology

Median endodermal derivative that migrates from the tongue base to its normal position in the neck by 7th week .

The distal portion of this thyroglossal duct forms the thyroid gland

Physiology

Concentrate iodine 20 – 30 % is store in thyroid Small percentage in hormone and nonthyroid

tissue All tyrosine compounds are bound to

thyroglubulin and store in thyroid follicles as colloid

The unbound thyroid hormone is responsible for influencing metabolism .

Thyroglossal duct anomaly

7% of the population has remnants of the thyroglossal duct

Cyst : anywhere along the length of duct

60% infrahyoid , 24% suprahyoid ,

1% intralingual 1-2 cm cystic mass that is mobile on

swallowing & protruding of the tongue

60% contain thyroid tissue Malignancy is rare Acute infection Contain mucus like clear fluid If it is become symptomatic it must be

removed Sistrunk operation

Lingual thyroid

Failure of thyroglossal duct to descend A mass at the foramen cecum Aysmptomatic or present with airway

obstruction May be the only thyroid tissue

Ectopic thyroid tissue

Anywhere along the migratory route of the thyroid

Mediastinum , larynx , trachea , pericardium or esophagus

Congenital intrathyroid cysts

Present in children persistent ultimobranchial bodies or an intrathyroidal thyroglossal duct cyst

Infectious and inflammatory disorder

Acute suppurative thyroiditis

M=F Preceded by an upper respiratory tract

infection Staph. The most common organism Painful enlargement of the gland Fever Abscess formation

Painless thyroiditis

Sporadic form

More common in female Difuse thyroid enlarement Without pain or thyroid enlargement Temporary hyperthyroidism 50% become hypothyroid which resolves in

6 month

Postpartum thyroiditis

Initial hypothyroidism is mild Lymphocytic infiltration and follicle disruption Self-limiting disease Steroid may be of value

Subacute thyroiditis ( De Quervain´thyroiditis )

At all age most common at 5th decade F>M May be viral Painful thyroiditis Defuse thyroid enlargement Malaise and fever thyrotoxic

Endocrine phases

Hyperthyroidism : 1-3 month Euthyroid : 1-3 weeks Hypothyroid : 2-6 month Recovery which is complete

Lymphocyte , monoycyte and giant cell infiltration .

Treatment consist of analgesic steroid and antiinflammatory agents .

Hashimoto´s thyroiditis

Common Affecting 2 population 95 % in female Autoimmune etiology with

strong genetic predisposition Diffusely enlarge with nodularity firm Disrupted follicle with lymphocyte and plasma

cell infiltration and variable fibrosis Residual hypothyroidism

A thyroid scan demonstrated a salt and pepper pattern

Anti thyroglobulin and antimicrosomsal ab are present up to 90%

FNA is diagnostic Increased risk for developing B – cell

lymphoma

Riedel‘s thyroiditis

Uncommon F>M Older patient May be mediastinal & retroperitoneal fibrosis Fixed rock-hard thyroid enlargement Gland replaced with fibrosisAirway obstruction and

dysphagia Palliative surgery to relieve obstruction

Hyperthyroidism

Graves‘ Disease

3th and 4th decade F/M : 7/1 Autoimmune etiology : abnormal Ig that fix on

TSH receptor of thyroid epithelial cell Diffuse toxic goiter ophthalmopathy 55% Dermophathy 5%

Cont.

↑ T3 , T4 , T3RU Thionamide , sympathetic blocker , iodine Radioactive iodine

Pregnant women should not be treated with this modility

Surgical indication

Refuse radioactive therapy Thyroid nodules suspicious for malignancy Must be rendered euthyroid prior to surgery

Subtotal thyroidectomy leaving 7-8 gr of nodule free tissue is recommended however ,

total thyroidectomy is proposed by many

Toxic multinodular goiter

Older patient no ophthalmopathy or dermophathy

Total thyroidectomy Radioactive iodine but not successfully as

surgery

Toxic adenoma

Younger patient Quite large ( 2.5 – 3 cm ) Surgical excision

Multinodular nontoxic goiter

Compensatory response Common in female Secondary to dietry

deficiency Symptom and sign of pressure

A small percentage (1-2%) may harbor a malignancy

Treatment

Thyroid suppression Surgery:

cosmetic deformity

pressure symptom refractory to suppression

Fear of malignancy

Development of toxicity

Neoplasm & Cyst

Benign adenoma

Encapsulated tumor Glandular epithelium with intratumoral

degenerative changes ( hemorrhage , fibrosis , calcification )

Rare thyrotoxicosis Type : follicular,colloid , embryonal, fetal ,

Hurthle ???

Malignant

Papillary carcinoma60 – 65 %

Third – 5th decade F/M : 2/1 Indolent with overall excellent prognosis May arise from benign adenoma Low-dose and high dose external RT

Macroscopic pattern

Occult ; <1.5 cm Intrathyroid ( 70% ) Extrathyroid : infiltrate larynx , trachea , strap

muscle , great vessel

Microscopic pattern

Purely papillary Some may have area of follicular Anaplastic transformation is rar Venous invasion in 10%

Intraglandular lymphatic invasion results in high incidence of multicentricity

Neither multicentricity nor regional LN metastasis have any prognostic

significance

Negative prognostic indicator

Advance age Male gender extrathyroid extension Distant metastasis

Cont.

Dedifferentiation Vascular invasion Atypical variants ( tall cell, columnar ,

sclerosing ) may have negative prognostic significance

Follicular carcinoma15%

Vascular invasion Metastasis to bone brain and liver Anaplastic transformation is more common Overtly invasive : infiltrate surrounding

structure ( MR 20-50%) Minimally invasive : microscopically has

capsular invasion (MR 5%)

Definitive diagnosis can often be established only on permanent section

Poor prognostic indicator

Advanced age Male gender extrathyroid extension Distant metastasis Vascular invasion anaplastic transformation trabecular growth

pattern

Hurthle cell carcinoma 5%

As a variant of follicular tumors Overtly invasive :higher mortality rate

Higher LN metastasis

Minimally invasive

Not all nodule containing Hurthle cell are neoplastic .The vast majority are Hurtule cell

changes in benign follicular adenomatous nodules or thyroiditis

Medullary carcinoma 3-5%

10 – 20 % familial Sporadic : in 5th decade Multicentric ,lateral upper 2/3 of gland Encapsulated , diffuse infiltrative 50% nodal metastasis 15-25% distant metastasis

MEN type 2A

Medullary thyroid cancer C-cell hyperplasia Adrenal pheochromocytoma Adrenal medullary hyperplasia Parathyroid hyperplasia

MEN type 2B

In addition : Mucosal neuromas GI ganglioneuroma Musculoskeletal abnormality

Poor prognostic indicator

MEN type 2B Nodal & distant metastasis Extrathyroid extension Small cell tumor pleomorphism Poor calcitonin staining High CEA

Anaplastic carcinoma 1-5%

Rare tumor Arise in well-differentiated tumor Older women Advance stage early infiltration of

surrounding structure Small cell , giant cell Extremely poor prognosis

Lymphoma 1-3.5%

Primarily in the thyroid As a part of systemic disease Arises in a gland with Hashimoto´s thyroiditis Elderly women Diffusely enlarged gland or nodule Hypothyroidism Diffuse large cell lymphoma Good prognosis

Miscellaneous

Sarcoma Mucoepidermoid carcinoma SCC Kidney , colon , melanoma are the most

common distant site

Clinical presentation

Thyroid enlargement

Smooth and diffuse ( usually benign ) Nodular Multinodular goiter may harbor a

neoplasm( 10-15% ) :

90% benign

10 % malignent

Overall incidence of malignancy in a multinodular goiter is only 1-2%

Symptom & sign of pressure

Dysphagia ( discomfort on swallowing → obstruction )

Mild to moderate stridor → chondromalacia → airway obstruction

TVC edema & RLN paralysis → hoarseness Retrosternal extension → tracheal deviation

& SVC

Symptom & sign of infiltration

Stridor and hemoptysis Rapid increasing in mass RLN paralysis Dysphagia & odynophagia Brachial plexus infiltration Painful enlargement

Evidence of regional and distant metastasis

It is the only obvious clinical evidence of thyroid cancer

Papillary metastasis may be cystic ( 20%) Follicular carcinoma : distant metastasis Medullary and anaplastic : extracapsular

extension

Evidence of endocrine dysfunction

Most patients are euthyroid Occasionally : hypothyroid Rarely : hyperthyroid Medullary : ↑ calcitonin , ACTH , PG

secretion

Evaluation of a thyroid mass

Neck X-ray

Patchy calcification :

Benign thyroid disease

Well –differentiated carcinoma

Medullary carcinoma

Chest X-Ray

Retrosternal extension Tracheal deviation Mediastinal nodal involvement Pulmonary metastasis

CXR should always be done

Esophagogram

It should be done if the patient complains of significant dysphagia

It differentiate thyroid from nonthyroid causes of dysphagia

Radionuclide scan

Determine the functional status of gland Differentiate diffusely enlarge from nodular Differentiate single nodule from multinodular

goiter

Tc-99

Low cost Ready available Short – half life Optimal imaging Only trapped , not organified

Radioactive Iodine

It is able to determine function ¹²³I is the best but is expensive and have

very short half life

Thallium 201

Detecting :

lymph node metastasis

retrosrernal extension

recurrent disease functioning nodule within suppressed gland

Octreotide scintigraphy is useful for detecting metastatic medullary and

Hurthle cell carcinoma

Radionuclide scan no longer used as a first line imaging study

Ultrasonography

High – resolution real time US enable the radiologist to detect nodule as small as

3mm

US usage

Screening high risk patient ( prior RT ) Differentiating single nodule from multiple Cystic or solid status Facilitating FNA Monitoring medically treated patient Evaluating clinically negative neck for

metastasis Recurrent disease after surgery

CT scaning & MRI

Extrathyroidal extension Retrosternal involvement Metastatic disease Unnecessary in the evaluation of a routine

thyroid mass

Metastatic workup

Bone scan CT scan of abdomen and chest Octreotide study

Blood test

T3 T4 TSH Thyroid Ab for Hashimoto thyroiditis Serum thyroglobulin Serum calcitonin in medullary carcinoma

especially if there is a family history

These level may increases after FNA and should be performed prior to it

Postoperative serum thyroglobulin levels under 10 ng/ml in patients under

supression therapy are indicative of cancer control

FNA biopsy

Obtain satisfactory specimen from nodule it is of no value in microinvasive follicular If the report is suspicious the patient should

probably proceed to surgery Inadequate specimen repeat FNA

FNA biopsy

The best results obtains from periphery Multiple aspirates are frequently necessary

A negative FNA should never preclude surgical exploration in a patient with

highly suspicious lesion

Large bore needle aspiration

A portion of capsule and surrounding tissue can be included

It is rarely indicated

Surgical exploration indication

Obvious malignancy

Clinical or radiographic evidence of infiltration

Clinical or radiographic evidence of regional or distant metastasis

FNA positive for malignancy ( papillary , medullary , anaplastic )

Thyroid mass with raised serum level of calcitonin

Suspicion of malignancy

Suspicious fine – needle aspiration Nodule refractory to suppression Solitary thyroid nodule with raised serum

thyroglobulin level Recurrent cyst refractory to two aspirations and

thyroid suppression Nodule going wrong , a solitary nodule increasing in

size and associated with pain True single nodule in males elderly women children ,

or in any patient with a history of prior RT

Management of thyroid Tumor

Every patient undergoing a thyroid exploration should sign a very specific

detail and inform that should include the possibility of performing throidectomy

Total thyroidectomy

Better oncologic operation in the case of multicentric disease

Difficult residual thyroid suppression and anaplastic transformation risk

Good postoperative scanning and radioactive ablation

Postoperative thyroglobulin titrage

Subtotal thyroidectomy

Simpler & time –consuming Lower morbidity Not affected the prognosis of well

differentiated tumor

Extrathyroid extension

Well-differentiated tumor : 9-16% If gross tumor would be left using the shaving

technique wild field resection should be performed .

RLN enveloped & paralyzed it should be sacrificed .

If it is the only functioning nerve and the tumor and the tumor can be dissected off this should be done

Superficial invasion can be shaved but direct extension into the lumen : sleeve

or wedge resection and primary anastomosis

Superficial thyroid cartilage : shave resection Hemilarynx : vertical partial laryngectomy Anterior larynx : hemilaryngectomy And

reconstruction Cricoid and bilateral laryngeal involvement :

total laryngectomy

Postoperative RT and iodine is indicated

Regional lymph node

In all patient : pericapsular and paratracheal node need to be removed routinely

Overt node in these area : sup. Mediastimun and lateral neck exploration

Papillary carcinoma

Clinical node : 20-25% Pathological node : 30-79% It has no adverse effect on prognosis Extracapsular extension does not appear to

have an ominous prognosis

Follicular carcinoma

Very rare < 10% clinically & 20% pathologically

Neck dissection are performed only for overt metastasis

Hurthle cell carcinoma

30% lymphatic metastasis Functional neck dissection should be

performed when disease is encountered

Medullary carcinoma

Metastasis : 50 – 63 % Prophylactic paratracheal , superior

mediastinal and lateral neck dissection Or : positive node in mediastinum and lateral

neck dissection is performed

Follow -up

Well-differentiated tumor

Become hypothyroid and after 4-6 week radioiodine scan

Any residual tissue : I ablation In overt local or regional remnant & distant

metastasis should be used Further 6 and 12 months scan and then

every 2 year Serum thyroglobulin every 6 months

Medullary carcinoma

Calcitonin level : every 3 months ( in first year )

Every six months there after High calcitonin level : full metastatic work up

CT & MRI of the neck and octreotide scan No overt disease : neck dissection and if it

done before RT to neck

Postoperative RT

Residual and inoperable disease or cancer that has undergone anaplastic transformation

50 Gy RT appears more effective than radioactive iodine in

treating local recurrence in WD cancer I radioactive is the treatment of choice for distant

metastasis RT is the treatment of choice in anaplastic carcinoma

Role of chemotherapy

Most disappointing results

Postoperative thyroid hormone

Total thyroid ablation : T4 supplement It is useful in controlling any microscopic

residual WD thyroid cancer that may have been left locally , regionally or distantly

Prognosis

Low risk patient : 1-2 % MR High risk patient : 40 – 50 % Hereditary & sporadic cancer have similar

survival ( 82% at 5 year ) Anaplastic cancer has a dismal survival Early stage medullary : good prognosis