Disorders in Thyroid Development Thyroglossal Duct Anomalies



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Disorders in Thyroid Development

1. Thyroglossal Duct Anomalies




Thyroglossal duct-cyst

Thyroglossal duct carcinoma

Ectopic thyroid

Location

Midline of neck ant to trachea

65% infrahyoid

20% suprahyoid

15% at hyoid bone



Less than 100 cases reported

90% base of tongue near foramen cecum (lingual thyroid)

Except medullary carcinoma all other thyroid lesions have been reported in this location

Gross

Cyst content: watery, mucoid, gel, pasty or purulent, 2-3 cm in diameter

Midline fluid filled cyst w/papillary excrescences

Solid or cystic w/hemorrhage

70% may be patients only thyroid tissue—do thyroid scan to confirm



Microscopic

Lining may be squamous, ciliated columnar, transitional or cuboidal w/surrounding lymphocytic infiltrate

Wall may contain thyroid tissue

Tract usu goes thru hyoid bone


Papillary structures, atypical follicles, psammoma bodies & fibrosis w/squam metaplasia

Benign ectopic thyroid follicles used as exclusion from metastatic tumor






treatment




Radical excision of entire tract including tumor and hyoid bone (sistrunk procedure)

Good prognosis






2. Lateral Aberrant Thyroid

  • Most are foci of follicular carcinoma or follicular variants of papillary carcinoma metastatic to neck lymph nodes

  • Tx: ipsilateral thyroid lobectomy

  • Sometimes benign thyroid particles seen in skeletal ms unassociated w/a lymph node

    • Migration of thyroid follicle to neck can occur in nodular goiter & Hashimotos’s

    • usu a surrounding lymphocytic infiltrate w/o architecture of lymph node


Chronic Thyroiditis




Hashimoto’s

Subacute (granulomatous)

Riedel’s struma

Subacute lymphocytes (painless)

Description

Most common form of chronic thyroditis & cause of non-endemic goitrous hypothyroid (also major cause in kids)

45-65 y.o women

10-20:1 more common in women


Women in 3rd-5th decade (3-5:1)

Enlarged thyroid, firm, tender, unilateral in 20%

Typical: sudden painful enlgment w/fever & viral infection


Exceedingly rare

Unilateral; woody hard thyroid (ligneous), nodular, densely adherent to surrounding structures




Most common in post-partum women

Uncommon cause of goitrous hyperthyroid, responsible for 1-10% of total hyperthyroid





Gross

classic

4X Symmetrically enlarged

Smooth, firm, not attached to surrounding structures

Gray, nodular w/septae, may be friable



Fibrous (atrophic)

10%; 1/3 of parenchyma may be replaced by bands of fibrous tissue

May resemble Riedels

Not adherent to surrounding


Diffuse: 2-3x enlg, firm, yellow white areas stand out from rubbery brown thyroid substance

Intact capsule, slightly adherent to surroundings but can be easily separated



Dense white scar where involuted part of thyroid was

Mild enlargement

Micro

Classic

Extensive infiltration of parenchyma by sm lymphocytes, plasma cells, well dev germinal ctrs

Many thyroid follicles destroyed

Remaing follicles are sm, lined w/epith cells w/eosinophilic cytoplasm=Hurthle cells

Delicate fibrosis-lobular pattern

Confined w/in thyroid capsule

Hyperplastic follicles in young adults

Fibrous

Extensive fibrosis w/follicular atrophy, few clumps of eosinophilic colloid

May not be recognized as thyroid

Hurthle cells & squam metaplasia



Early: scattered follicles replaced by microabscesses

Late:lymphocytes aggregates. Plasma cells, histocytes around collapsed & damaged thyroid follicles

Multinuc giant cells enclose colloid

End stage: chronic inflamm infiltrate & fibrosis


Waves of destruction—diff stages found in one gland

Thyroid tissue is completely replaced by mature hyalinized collagen
No prominent inflammation
Diff dx:

  1. thyroid carcinoma

  2. fibrous variant Hashimoto’s

frozen section would help diff from carcinoma



Infiltration by small lymphocytes with patchy disruption and collapse of thyroid follicles.

Rare plasma cells, no germinal centers



Pathogenesis

Autoimmune disorder both humoral & cell mediated injury cause damage to thyroid gland

Post viral inflamm process

Self limited

HLA-B35


Some occur in pts w/idiopathic retrop fibrosis, mediastinal fibrosis, sclerosing cholangitis, pseudotumor of orbit

unknown

course

Myxedema may develop after yrs due to progressive destruction of parenchyma

Not precancerous, but ↑risk B cell lymphoma



Pain in neck may radiate to jaw, ears; fever, fatigue, malaise, anorexia, myalgia w/variable enlgment of thyroid

May Present w/asphyxia due to the pressure on the trachea

Self-limited, no sequelae

No hx. of viral infection

Common hyperthyroid sx. Develop over 1-2 wks, and last 2-8 wks.


Treatment

Thyroid hormone

Do not do subtotal thyroidectomy

Self-limited;

almost always complete recovery



Surgery difficult

Self-limited


Goiter

  • any enlargement of part or whole of the thyroid gland secondary to impaired synthesis of TH and compensatory response in serum TSH

  • TSH response causes hyperplasia and hypertrophy of thyroid follicular cells

  • Two types

  1. Endemic type – more common

    • From iodine deficiency in food or water in mountainous areas of the world

  2. Sporadic type

  • Less common than endemic

  • Females> males, 8:1

  • Minimal iodine lack w/increased demand for TH

  • In indiv residing in areas w/adequate iodine

  • Cause unknown

    • Hereditary Aut Rec enzymatic defects

    • Dietary goitrogens (substances that interfere w/thyroid hormone synthesis cabbage, cauliflower, brussel sprouts, turnips)




Simple (diffuse, non-toxic, colloid)

Multinodular – premalignant to follicular carcinoma

Gross

Diffuse, moderately enlarged and vascular

Not assoc w/hyper or hypofunction



Nodular enlgment involving either part or whole thyroid

Cut surface: variegated pattern due to hemorrhage, calcification, fibrosis, microcyst formation

May reach enormous size (up to 2000g) & show retrosternal prolongation


Micro

Early: hyperplastic stage—hypertrophy & hyperplasia of follicular epithelium w/scant colloid

Later: if dietary iodine ↑ or demand for TH↓, the stimulated follicular epith involutes to form enlarged colloid rich acini lined by low cuboidal to columnar epithelium (colloid goiter)



Follicles of varying sizes grouped together in form of ill defined nodules which may be separated by broad bands of fibrous tissue w/old hemorrhage & calcification
Focal papillary hyperplasia may not be associated w/hyperthyroidism

Course

Children: caused by congenital biosyn defect may cause cretinism

Adults: achieve state of euthyroidism; few hyperthyroid



Usually follows recurrent episodes of stimulation and involution of diffuse goiter, causing irregular enlgment of thyroid

Most long standing simple convert to multinodular



complications




Pressure on trachea, esophagus, SVC

Hemorrhage w/rapid ↑size may lead to asphyxia

Hypethyroidism from a toxic nodular goiter (plummer’s syndrome)—not accompanied by infiltrative ophthalmopathy & dermatopathy like graves.

Hypothyroidism is rare, typically euthyroid

Radioiodine uptake is uneven

Distinction b/t multinodular and neoplasm is difficult in dominant nodule




Hyperthyroidism & Grave’s Disease

  • Common 1.5-2% women in US

  • Hyperthyroidism from protracted high levels of TH which can been seen in diffuse hyperplasia, toxic nodular goiter, toxic adenoma

  • Diffuse hyperplasia or Grave’s disease peak age 20-40yrs, 7:1 more common in women


Grave’s Disease

  • Most common cause of endogenous hyperthyroidism

  • No increased risk of cancer

  • Characterized by triad

  1. Hyperthyroidism

  2. infiltrative ophthalmology

  3. Dermatopathy (thickening and induration of skin), only in 10-15%

  • Pathogenesis: autoimmune—Ab’s to TSH receptor or TSI

  • Gross: diffusely enlarged vascular meaty gland w/smooth capsule

  • Microscopic: small acini w/tall columnar hyperplastic cells w/papillary projections

    • Acini—diminished colloid, scalloping margins

    • Vascularity & lymphocytic infiltration w/follicles w/in interfollicular parenchyma

    • Audible bruit due to increased blood flow

  • Clinical:

    • generalized lymphoid hyperplasia, hypertrophied heart, & ischemic changes if have pre-existing CAD

    • Increased metabolism – weight loss, increased sweating

    • Cardiovascular effects – tachycardia, increased CO, arrhythmias, cardiac failure

    • Neurological effects – mood swings, tremor, myopathy

    • Eye signs – exopthalmos, lid retraction

    • Skin edema – pre-tibial myxedema

  • Labs:

    • ↑free T4 and T3

    • ↓TSH

    • ↑radioactive iodine uptake (b/c of follicle stimulation by thyroid stimulating immunoglobulins-TSI)

  • Treatment:

    • Surgical—subtotal thyroidectomy

    • Medical—decrease TH synthesis by radioiodine ablation

  • Course: Tx may result in control of hyperthyroidism but eye changes may remit, persist, or progress


Tumors of the Thyroid

Adenomas

  • Most common benign thyroid tumor, arising from the follicular epithelium

  • Single nodule, well defined capsule surrounding uniform epithelial cells that are diff from surrounding normal thyroid

  • Presents as painless mass which must be differentiated from a carcinoma

  • Take up less radio-iodine than normal parenchyma – cold on scans (can be exceptions)

  • 10% of cold adenomas are malignant – use FNA to help evaluate, but definitively need microscopy

  • Slowly increase in size – can get pressure symptoms, remain stable, suddenly increase in size with pain due to hemorrhage




Follicular

papillary

Atypical (spindle cell)

Hurthle cell

description

Most common thyroid adenoma

Composed of thyroid acini of varying sizes w/zone of fibrosis & hemorrhage in center

Types: Trabecular, fetal, colloid


No true papillary adenoma

Most are papillary carcinoma



Encapsulated tumor showing tightly packed spindle cells w/↑ cellularity, mitosis, & atypia

No capsular or vascular invasion

Some w/follicular pattern w/pleomorphic nuclei


Follicular adenomas w/acini composed of granular eosinophilic cells w/lots mitochondria


Carcinomas




Papillary

Follicular

Medullary

Undifferentiated (anaplastic)

description

Most common type of thyroid ca

Only 3.3% are pure papillary

Most mix of papillary, follicular, solid

Spreads via lymphatics

Many assoc w/prior ionizing radiation exposure

Ave age 2nd-4th decade; females

Five forms

~Minute clinically occult (small scar, seen in many autopsies)

~Larger infiltrating (gray, firm, can be calcified, have cystic change, or extend into peri-thyroidal tissue)

~Encapsulated (rare spread, excellent prognosis)

~Follicular (nuclear features important)

~Tall cell (eosinophilic cells, vascular invasion, metastasis, older individuals, worse prognosis)



10-20% of all thyroid carcinomas

50 yrs. old, more in women

Increased prevalence in iodine deficient areas
Grossly – variegated, pink with red-brown areas of hemorrhage, necrosis, calcification, cysts formation. If invasive, may see gross infiltration of surroundings


NO psamomma bodies, empty nuclei, nuclear grooves, eosinophilic intranuclear inclusions


5% of all thyroid cancers

Peaks at 40-50 in sporadic, 20-30 in familial

~C cell (calcitonin secreting) tumor

~Many with amyloid in stroma

~Familial – MEN IIA and IIB

MEN IIA – Sipple syndrome.

Aut dom.

Medullary carcinoma, C-cell hyperplasia, adrenal pheochromocytoma, adrenal med. Hyperplasia, parathyroid hyperplasia

Ret oncogene mut. On chromosome 10



MEN IIB

Medullary carcinoma, C-cell hyperplasia, pheochromocytoma, adrenal med. Hyperplasia, mucosal neuromas, GI ganglioneuromas, MSK abnormalities

Very aggressive, many metastases

Neural lesions often precede medullary cancer


Gross – gray-white, solitary, firm, well-circumscribes. If familial, may be bilateral

Less than 5%

~Most common in elderly, often in areas of endemic goiter

~Rapidly progressing neck mass, which can cause hoarseness, SOB, stridor

~Tumor infiltrates skeletal muscle, may extend posterior to trachea, into upper mediastinum.

~Aggressive, with CLN and lung metastases

~Sometimes, see foci of papillary or follicular differentiation, suggesting origin from better differentiated carcinoma





microscopic

Variable pattern w/well defined papillae & fibrovascular cores

Cells may have

-hypochromic empty nuclei w/o nucleoli (orphan annie eyes)

-nuclear grooves

-eosinophillic cytoplasmic invag into nuclei
Psammoma bodies in 50%


Microfollicular growth pattern, solid and trabecular areas present.

Encapsulated form looks very normal

Can be composed entirely of Hurthle cells

Invasive form – hematogenous spread, lots of mitosis, necrosis, obviously malignant



Tumor cells may be round, spindle shaped, plasmacytoid with a nesting, pseudofollicular, or trabecular pattern
May be amyloid.
Foci of c-cell proliferation in familia but usually not in sporadic.
Calcitonin is demonstrable by immunohistochemical stains.

Highly anaplastic cells, with following patterns:

~large, pleomorphic giant cells

~spindle cells with sarcomatous appearance

~small anaplastic cells





Tx & prog


Multifocal in 20-80%

CLN metastases in 50% at dx.

Tx varies: total thyroidectomy, ipsi


Unilateral lobectomy

Encapsulated – slow growing, spread by blood, hot spot. Metastases may appear years after excision of primary

Invasive – metastatic to liver, lung, bone in 50%

More aggressive, worse prognosis than pap



Good if detected early enough. Malignant nodules may be very small.

Dismal – median survival of 6 mo.


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