Pathology: Thyroid II

Question 1

What is a thyroglossal duct cyst?

Answer 1

Cystic dilation of thyrogossal duct remnant

• Presents as anterior neck mass

Question 2

Wha is lingual thyroid?

Answer 2

• *Persistence of thyroid tissue at base of tongue**
• Don’t get embryological descent of thyroid through thyroglossal duct
• Presents as a base of tongue mass

Question 3

What is Hyperthyroidism?

Answer 3

Increased level of circulating thyroid hormone

• Increase basal metabolic rate by increasing synthesis of Na/K ATPase
• Increases sympathetic nervous sytem activity due to expression of B1 adrenergic receptors

Question 4

What are clinical features of hyperthyroidism?

Answer 4

• Weight loss despite increased appetite
• Heat intolerance and sweating
• Tachycardia with increased cardiac output
• Arrhythmia (esp. in elderly)
• Tremor, anxiety, insomnia, and heightened emotions
• Staring gaze with lid lag
• Diarrhea with malabsorption
• Oligomenorrhea
• Bone resorption with hypercalcemia (can lead to osteoporosis)
• Decreased muscle mass with weakness
• Hypocholesterolemia
• Hyperglycemia

Question 5

What is most common cause of hyperthyroidism?

Answer 5

Graves Disease

• Autoantibody (IgG) that stimulates TSH receptors
• Leads to increased synthesis and release of thyroid hormone
• Occurs in women of childbearing age

Question 6

What are clinical features of Graves Diseaes?

Answer 6

Hyperthyroidism

Diffuse Goiter

Exophthalmos and pretibial myxedema (due to IgG activation of TSH receptors at these sites causing production of excess glycosaminoglycans)

Question 7

What are lab features of Graves Disease?

Answer 7

- Increased total and free T₄

- Decreased TSH (T₄ down regulates TRH receptors on anterior pituitary)

- Hypocholesterolemia

- Increased serum glucose

- “Scalloping” histology of thryoid follicles

Question 8

What is the treatment for Graves disease?

Answer 8

Beta-blockers

Thioamide (blocks production of T₄)

Radioiodine ablation

Question 9

What is thyroid storm?

Answer 9

Feared Complication of Graves Disease

• Elevated catecholamines and massive hormone excess (stress)
• Arrhythmia, hyperthermia, and vomiting with hypovolemic shock
• Treted with PTU, Beta-blockers, and steroids

Question 10

What is a multinodular goiter?

Answer 10

Enlarged thyroid gland with multiple nodules

• Due to relative iodine deficiency
• Usually nontoxic (euthyroid)
• Rarely, regions become TSH-independent (“toxic goiter”)

Question 11

What is Cretinism? What are its symptoms?

Answer 11

Hypothyroidism in neonates and infants

Clinical Features:
Mental Retardation
Short Stature with skeletal abnormalities
Coarse facial features
Enlarged tongue
Umbilical hernia

Question 12

What are causes of Cretinism?

Answer 12

• Maternal hypothyroidism during early pregnancy
• Thyroid agenesis
• Dyshormonogenetic goiter
• Iodine deficiency

Question 13

What is myxedema? Clinical features?

Answer 13

Hypothyroidism in older children or adults

• *Clinical Features:**
• Myxedema (edema has “dough-like” consistency)
• Larynx –> deepening of voice
• Enlarged tongue
• Weight gain despite normal appetite
• Slowing of mental activity
• Muscle weakness
• Cold intolerance with decreased sweating
• Bradycardia with decreased cardiac output
• Oligomenorrhea
• Hypercholesterolemia
• Constipation

Question 14

What are causes of Myxedema?

Answer 14

Iodine Deficiency

Hashimoto Thyroiditis (autoimmune destruction of thryoid gland

Drugs (i.e. lithium)

Surgical removal or radioablation of thyroid

Question 15

What is Hashimoto Thyroiditis?

Answer 15

Autoimmune destruction of thyroid gland

• Associated with HLA-DR5

Question 16

What are clinical features of Hashimoto Thyroiditis?

Answer 16

Initially may present as hyperthyroidism (due to initial destruction of cells and abundant release of T₄)

• Passes a point of normal thyroid regulation then:

- Progresses to hypothyroidism (decreased T₄ and Increased TSH)

- Antithyroglobulin and antimicrosomal antibodies are often present (signs of thyroid damage)

- Chronic inflammation with formation of germinal centers and hurthle cells, histologically

Question 17

What is Subacute (deQuervain) Granulomatous thyroiditis?

Answer 17

• Granulomatous thyroiditis that follows a viiral infection
• Presents as tender thyroid with transient hyperthyroidism
• Self-limited; does not progress to hypothyroidism

Question 18

What is Reidel Fibrosing Thyroiditis?

Answer 18

• Chronic inflammation with extensive fibrosis of thyroid
• Presents as hypothyroidism with ‘hard as wood’ nontender thyroid gland
• Fibrosis may extend to local structures (i.e. airway)

–> Classically a young female

Question 19

What is a 131I radioactive uptake study?

Answer 19

Completed to help diagnose thyroid nodules

• Increaed uptake of ¹³¹I seen in Graves or nodula goiter
• Decreased uptake of ¹³¹I seen in adenoma and carcinoma (warrants FNA - fine needle aspiration - biopsy)

Question 20

What is a follicular adenoma?

Answer 20

Benign proliferation of follicles surrounded by a fibrous capsule

• Usually nonfunctional; rarely may secrete thyroid hormone

Question 21

What are the four types of thyroid carcinomas?

Answer 21

Papillary Carcinoma (*Most Common* = 80%)

Follicular Carcinoma

Medullary Carcinoma

Anaplastic Carcinoma

Question 22

What is a major risk factor for papillary carcinoma?

Answer 22

Exposure to ionizing radiation in childhood

Question 23

What are histological signs of papillary carcinoma?

Answer 23

Production of papillary structures

• Presence of “orphan annie-eyed” nuclei
• Presence of nuclear grooves
• Calcification of papillary architecture leads to psammoma bodies

Question 24

Where does papillary carcinoma of the thyroid spread?

Answer 24

Cervical lymph nodes

• however, even with lymph node spread, there is an excellent prognosis

Question 25

What is follicular carcinoma? Where does it metastesize to?

Answer 25

Malignant proliferation of follicles in the thyroid

• Surrounded by a fibrous capsule with invasion through capsule –> FNA cannot distinguish between follicular adenoma and follicular carcinoma
• Generally goes into blood (hematogenous metastesis)

Question 26

What is medullary carcinoma?

Answer 26

- Malignant proliferation of parafollicular C cells

- High levels of calcitonin produced by tumor may lead to hypocalcemia

- Calcitonin often deposits within tumor as amyloid (localized amyloidosis)

Question 27

What are familial cases of medullary carcinoma associated with?

Answer 27

Multiple Endocrine Neoplasia (MEN) 2A and 2B

–> RET oncogene

Detection of RET mutation warrants prophylactic thyroidectomy

Question 28

What is anaplastic carcinoma?

Answer 28

Undifferentiated malignant tumor of thyroid

• Usually seen in elderly
• Often invades local structures leading to dysphagia or respiratory compromise
• poor prognosis
• Clinically similar to Reidels thyroiditis (which is seen in younger patients)