Pathology of Thyroid

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1 : The Pathology of the Thyroid gland Dr Niranthi Perera Senior lecturer
2 : Objectives You should be able to list the causes of goitre discuss the pathogenesis of diffuse non-toxic, colloid and multinodular goitre understand the changes which occur in the thyroid gland in the hyper and hypothyroid states
3 : Objectives - ctd 4. describe the different types of thyroiditis and their clinical significance 5. understand how to investigate a thyroid nodule 6. know the common thyroid malignancies and their clinical and prognostic relevance.
4 : Anatomy and physiology 2 lateral lobes with a midline isthmus Closely packed follicles with colloid Colloid contains thyroglobulin, T3, T4 Intervening stroma contains blood vessels and parafollicular C cells Gland takes up iodide, converts it to iodine, forms tyrosine residues,and links them to thyroglobulin forming T3, T4
5 : Causes of goitre Endemic goitre – soil, water and food in mountainous areas has a low iodine content 2. Sporadic goitre – increased demand in puberty or pregnancy 3. Hereditary enzyme defects 4. Goitrogens in cabbage, cauliflower 5. Drugs
6 : Multinodular goitre Commonest cause of an enlarged thyroid gland Sporadic or endemic Reflects an impaired synthesis of thyroid hormone, often due to dietary iodine deficiency. Impaired hormone synthesis TSH gross gland hypertr and hyperpl enlargement of thyroid follicular cells
7 : Pathogenesis of multinodular goitre I2 T3,T4 TSH Results of increased TSH Hypertrophy and hyperplasia of follicular cells – early stage - hyperplastic Initially, diffuse non-toxic goitre
8 : If transient dietary increase in iodine T3, T4 TSH This results on involution in the gland. Later, follicles are distended with colloid (colloid goitre)
9 : Colloid goitre
10 : With time, recurrent episodes of stimulation and involution of the gland irregular thyroid enlargement with nodule formation regenerative change - fibrosis, haemorrhage, calcification, cyst formation
11 : Multinodular goitre
12 : In a multinodular goitre, a hyperfunctioning toxic nodule may develop (autonomous toxic nodule) Produce hormones independent of TSH stimulation These patients have hyperthyroidism clinically A dominant nodule can mimic a neoplasm clinically
13 : Hyperthyroidism Hypermetabolic state Elevated circulating free T3 and T4 Diagnosis -- clinical features laboratory findings sTSH – most useful single screening test
14 : Grave’s disease Commoner in females 15-40 yrs Familial association with other AI diseases Triad of hyperthyroidism, infiltrative ophthalmopathy, and dermatopathy Pathogenesis – auto antibodies to TSH receptor
15 : Grave’s disease
16 : Hypothyroidism Structural or functional disorder interfering with hormone synthesis Causes 1. Post-surgical, post radioiodine treatment 2. Hashimoto’s thyroiditis 3. Iodine deficiency 4. Congenital biosynthetic defects 5. Pituitary or hypothalamic failure s TSH – most sensitive screening test
17 : Thyroiditis Inflammation of the thyroid gland May be classified on a. degree of rapidity –acute, subacute, or chronic b. predominant inflammatory response - polymorphonuclear, lymphocytic, granulomatous
18 : Chronic lymphocytic thyroiditis (Hashimoto’s disease) Autoimmune inflammatory disorder Also associated with other AI disorders Predominantly in older females Pathogenesis related to parenchymal destruction by CD 8 cytotoxic T cells (also involves autoantibody formation) Risk of B- cell Non Hodgkins Lymphoma
19 : Pathogenesis Early stage disruption of release of thyroid follicles hormones TSH T3, T4 Later as hypothyroidism supervenes T3, T4 TSH
20 : Hashimoto’s thyroiditis
21 : Hashimoto’s thyroiditis
22 : Subacute granulomatous thyroiditis (DeQuervain’s thyroiditis) Commoner in females, 30 – 50 yrs Pain in neck or pain on swallowing Preceding URTI. ? Viral aetiology One or more lobes enlarged Granulomatous reaction to ruptured colloid, with polymorphs, Lymphcytes , pl cells Transient hyperthyroidism due to released T3, T4 Raised ESR. Self-limited. Euthyroid in 6-8 wks.
23 : Granulomatous thyroiditis
24 : Granulomatous thyroiditis
25 : Riedel’s thyroiditis Rare Hard thyroid mass. Clinically simulates a neoplasm Circulating anti-thyroid antibodies seen Gland shows extensive fibrosis
26 : Riedel’s thyroiditis
27 : Riedel’s thyroiditis
28 : thyroid nodules In general, Solitary nodules are more likely to be neoplastic. Solid nodules are more likely to be neoplastic “Cold” nodules are more likely to be neoplastic “Hot” nodules are more likely to be benign.
29 : Follicular adenoma Benign Solitary Well-formed capsule Cold nodule on imaging Can be distinguished from a follicular carcinoma only on histology (not on FNA)
30 : Follicular adenoma
31 : Thyroid carcinomas Papillary carcinoma Follicular carcinoma Medullary carcinoma Anaplastic carcinoma
32 : Pathogenesis of thyroid carcinoma 1. Genetic factors Familial medullary carc in MEN (type 2) 2. Ionising radiation Foll: radiation treatment for head and neck malignancies, thyroid carcinomas develop years later Foll: exposure to IR after Chernobyl Nuclear plant disaster, they developed paillary carcinoma
33 : Papillary carcinoma Commonest form of thyroid cancer Painless mass in neck Can occur at any age Commonest cancer associatede with radiation Metastases via lymphatics Prognosis good, even with isolated cervival nodes
34 : Papillary carcinoma
35 : Papillary carcinoma
36 : Follicular carcinoma Present at an older age group to pap. Ca Well-circumscribed or infiltrative Metastasise through blood stream to lungs, bone, liver Prognosis is poorer than in papillary carcinoma
37 : Follicular carcinoma
38 : Follicular carcinoma
39 : Medullary carcinoma Neuroendocrine neoplasm derived from the parafollicular C cells Secrete calcitonin -useful in diagnosis and follow up Solitary nodule or multiple lesions May contain amyloid
40 : Medullary carcinoma
41 : Medullary carcinoma
42 : Anaplastic carcinoma One of the most aggressive of malignancies Found in the elderly Bulky, rapidly growing tissue mass in neck Metastases are common Death is usually from aggressive local growth, compromising vital structures in the neck.
43 : Fine-needle aspiration of the thyroid first-line procedure in investigating a thyroid nodule Indications 1. to distinguish malignant or possibly malignant nodules (which require surgical excision), from benign nodules that may be followed up clinically 2. in the evaluation of a diffuse goitre
44 : FNA - method 23 G needle and 10 ml syringe Supine patient with neck extended Gland immobilised against the trachea, as the aspiration is done rapidly Fine needle sampling may be done with or without the use of a syringe Needle contents are expressed on a slide
45 : FNA - ctd Aspirated material is smeared and fixed in 95% ethanol (wet smear) or air dried. The slide is stained with MGG, haematoxylin and eosin stain, and Papanicolau stain.


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