Thyroid Pathology Flashcards by Martha Innes

What is the location of the thyroid gland?

In the anterior neck below the larynx along the thyroglossal duct

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What is the histological structure of the thyroid gland?

Composed of lobules containing follicles defined by thin fibrous septa
Each follicle is surrounded by follicular epithelial cells
There are C cells (parafollicular cells) scattered about - these are slightly larger cells with clearer cytoplasm

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What is the function of follicular cells?

Secrete thyroglobulin
Produce colloid and thyroid hormones
Control the release of these hormones into the blood

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What is the function of C cells?

Secrete calcitonin

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What is the process of secretion of thyroid hormones?

TSH from the pituitary gland binds to TSH G-protein coupled receptors on thyroid epithelial cells
This causes an increase in the production of cAMP
cAMP increases production and release of T3 and T4

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What is the function of T3 and T4?

Bind to rage cells to increase basal metabolic rate

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Describe the negative feedback effect that controls the secretion of thyroid hormones.

Hypothalamus releases TRH which stimulates the anterior pituitary gland to secrete TSH
TSH stimulates thyroid follicular epithelium to secrete T3 and T4
Increased levels of T3 and T4 inhibit the anterior pituitary gland and the hypothalamus to decrease the secretion of TSH and TRH

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What do TRH and TSH stand for?

TRH - thyrotropin releasing hormone

TSH - thyroid stimulating hormone

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What are the main examples of autoimmune thyroiditis?

Hashimoto’s thyroiditis (hypofunction)

Grave’s disease (hyperfunction)

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What are the common features of autoimmune thyroiditis?

Increased incidence in family members
Susceptibility associated with the HLA haplotype
Association with other autoimmune diseases

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What are non-immune related causes of inflammation of the thyroid?

Palpation
Subacute lymphocytic
De Quervain's 
Infection
Riedel's

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What is thyrotoxicosis?

When symptoms and signs occur as a result of excess T3 and T4

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What are the causes of thyrotoxicosis?

Hyperthyroidism
Hyperfunctioning nodules and tumours
TSH secreting pituitary adenomas
Thyroiditis
Ectopic production
Facticious

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What is Grave’s disease?

An autoimmune disorder of thyroid gland hyperactivity

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Who are commonly affected by Grave’s disease?

Women (10 times more than men)

20-40 years old

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What is the action of anti-TSH receptor antibodies?

Act to stimulate receptors and mimic the effect of TSH

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What are the anti-TSH receptor antibodies?

Thyroid stimulating immunoglobulin
Thyroid growth stimulating immunoglobulin
TSH binding inhibitor immunoglobulin

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What triad of features are classic of Grave’s disease?

Diffuse enlargement of the thyroid
Eye changes (exophthalmus)
Pretibial myxoedema

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Which histological changes occur in Grave’s disease?

Most follicles contain little or no thyroglobulin, and where there is thyroglobulin, there aren areas of pallor at the edges
In between follicles is abundant lymphocyte invasion

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What is hypothyroidism?

Symptoms and signs due to low levels of T3 and T4

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What are the causes of hypothyroidism?

Hashimoto's thyroiditis (autoimmune)
Iodine deficiency
Drugs (e.g. lithium)
Post-therapy (surgery, irradiation)
Congenital abnormalities
Born errors of metabolism

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What are secondary and tertiary hypothyroidism?

A result of pituitary or hypothalamus pathology respectively

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What is Hashimoto’s thyroiditis?

Gradual failure of thyroid function?

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Who commonly present with Hashimoto’s thyroiditis?

Women (10-20 times more than men)

45-60 years old

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Which antibodies are associated with Hashimoto's thyroiditis?

Anti-thyroid antibodies (anti-thyroglobulin and anti-peroxidase)

What is the pathogenesis of Hashimoto's thyroiditis?

CD8+ cells cause destruction of thyroid epithelium Cytokines recruit macrophages that damage thyroid follicles Thyroid follicles atrophy Progressive fibrosis

What histological features can be seen in Hashimoto's thyroiditis?

Prominent lymphoid infiltration Lymphoid follicles with reactive appearing germinal centres Islands of residual normal thyroid follicles containing thyroglobulin

What may precede hypothyroidism?

Transient hyperfunction (Hashitoxicosis)

What is there an increased risk of in Hashimoto's thyroiditis?

B cell non-Hodgekin's lymphoma

What is a goitre?

Any enlargement of the thyroid gland

What are goitres usually caused by?

Lack of dietary iodine | Lack of bioavailability of iodine

How does a goitre form?

Reduced T3/T4 production causes rise in TSH, stimulating gland enlargement

Who commonly present with diffuse goitres?

Women | Puberty-aged and young adults

What will thyroid hormone levels be like in a diffuse goitre?

T3 and T4 usually normal | TSH often high or upper limit of normal

What are the different types of goitre?

Diffuse | Multi-nodular

What is a multi-nodular goitre?

One that has evolved from a long-standing simple goitre due to recurrent hyperplasia and involution

What effects can a large multi-nodular goitre cause?

Airway obstruction Dysphagia Compression of vessels

What are the thyroid neoplasms?

``` Follicular adenoma Papillary carcinoma Follicular carcinoma Medullary carcinoma Anaplastic carcinoma ```

What is the description of a follicular adenoma?

Discrete solitary mass

What are the symptoms of a follicular adenoma?

Usually asymptomatic and incidental finding | Local symptoms e.g. dysphagia if large

What is the pathology of a follicular adenoma?

Encapsulated by a surrounding collagen cuff Composed of neoplastic thyroid follicles Usually non-function but can secrete thyroid hormones

What are follicular adenoma usually caused by?

Mutations of the TSHR signalling pathway

What is themes common thyroid carcinoma?

Papillary carcinoma

What are the causes of thyroid carcinomas?

``` Ionising radiation (papillary carcinoma) Iodine deficiency (follicular carcinoma) MEN2 (medullary carcinoma) ```

Describe the pathology of papillary carcinomas

Usually a solitary nodule in the thyroid, can be multifactorial, often cystic, may be calcified

What are the symptoms and signs of papillary carcinomas?

``` Lesion in the thyroid gland or cervical lymph node mass Hoarseness Dysphagia Cough Dysphnoea ```

How do papillary carcinomas spread?

Lymph node metastasis | Uncommonly haematogenous spread, usually to lung

What is the prognosis for papillary carcinomas?

Good - survival at 10 years is 95%+ | Prognosis worse as age increases, if there is extra-thyroid extension or if distant metastases

Who commonly present with follicular carcinomas?

Women | 40s and 50s

Describe the pathology of follicular carcinomas

Usually a single nodule | Slowly enlarging, painless, non-functional

What is the spread of follicular carcinomas?

Rarely lymphatic spread | Can have haematogenous spread to bone, lungs, liver

Do follicular carcinomas commonly spread locally?

Yes - can be widely or minimally invasive

What are features of a widely invasive follicular carcinoma?

More solid architechture Less follicular architecture More mitotic activity

What are the features of a minimally invasive follicular carcinoma?

Follicular architecture (well differentiated) May have part surrounding capsule Difficult to distinguish from adenoma

What is the prognosis of follicular carcinomas?

Depends on extent of invasion and stage at presentation If high stage - 50% mortality at 10 years If minimally invasive - >90% survival at 10 years

What do medullary thyroid carcinomas derive from?

C cells

What are the types of medullary thyroid carcinomas?

Sporadic (70%) Associated with multiple endocrine neoplasia (MEN2a or 2b) Familial medullary carcinoma

Who usually presents with medullary thyroid carcinomas?

Can be very young if associated with MEN | Adults in 40s and 50s

What is the difference between sporadic and familial medullary thyroid carcinomas?

Sporadic - solitary nodules | Familial - bilateral or multicentric

Describe the pathology of medullary thyroid carcinomas?

Composed of spindle or polygonal cells arranged in nests, trabeculae or follicles

How do medullary thyroid carcinomas present?

``` Neck mass with local effects (dysphagia, hoarseness, airway compromise) Paraneoplastic syndrome (diarrhoea, Cushing's) ```

What is the treatment for medullary thyroid carcinomas?

Total thyroidectomy

What is the prognosis for medullary thyroid carcinomas?

5 and 10 year survival overall about 80% and 73% | 35% recurrence in patients who get a total thyroidectomy

What are the good and poor prognostic factors for medullary thyroid carcinomas?

Good: young age, female, small tumour size, confined to thyroid with no meastases Poor: necrosis, many mitosis, squamous metaplasia, MEN2b

What are anapaestic carcinomas?

Undifferentiated and aggressive tumours Usually present in older patients Can occur in patients with history of differentiated thyroid carcinoma Rapid growth and involvement of neck structures

Thyroid Pathology Flashcards

(65 cards)