Week 3: Pathology of the thyroid

Question 1

Congenital anomalies of thyroid

Answer 1

1. Athyreosis: complete absence of thyroid gland. results in cretinism if not caught early and treated.
2. Aberrant thyroid: abnormal embryologic migration, may leave thyroid rudiment in base of tone, upper neck or mediastinum
3. Thyroglossal duct cysts
   - failure of involution of stalk
   - midline cysts near hyoid bone
4. metabolic defects
   - Dyshormonogenic
   - defect in synthesis of thyroid hormones, results in high TSh with goiter formation

Question 2

Diffuse goiter

Answer 2

• symmetrically enlarged thyroid without nodules
• usually progresses to multi nodular goiter
• Etiology: iodine deficiency, dyshormonogenetic, sporadic (adolescence, pregnancy), goitrogens
• usually euthyroid, some hypothyroid
• due to increase TRH, TSh

Question 3

Multinodular goiter

Answer 3

• usually euthyroid but have mechanical (pressure)/cosmetic complaints
• gross: may have calcification, hemorrhage, fibrosis, cystic change
• microscopic: macro and microfollicles, colloid lakes, hemorrhage, fibrosis, calcification, cholesterol crystals, adenomatous proliferation and hyperplasia

Question 4

Graves disease

Answer 4

• gross: red, enlarged gland, meaty cut surface
• microscopic: hyperplasia, hypertrophy, tall columnar follicular cells. Scalloped and scant colloid
  1. diffuse goiter
  2. hyperthyroidism
  3. exopthalmos and/or pretrial dermopathy

Question 5

Hashimoto thyroiditis

Answer 5

• autoimmune, primarily T cell defect with circulating cellular and humoral antibodies
• diffuse, symmetrical goiter
• gross: pale, firm, rubbery, tan, or white
• microscopic: lymphocyte and plasma cell infiltration with germinal centers and fibrosis. Pink, plump granular oxyphil epithelial cells (Hurtle cells)

Question 6

Granulomatous thyroiditis aka subacute thyroiditis

Answer 6

• females more commonly affected
• viral origin is most likely, often hx of URI
• tender thyromegaly, fever
• microscopic: focal, granulomatous inflammation with giant cells engulfing colloid

Question 7

Riedel thyroiditis

Answer 7

• rare,
• rock hard thyroid stuck to neck structures
• microscopic: dense collagen containing chronic inflammatory cells and only a few scattered follicles
• may have idiopathic fibrosis elsewhere
• surgical removal for relief of compression

Question 8

Atrophy of thyroid

Answer 8

1. idiopathic-myxedema of adults
   - end result of chronic thyroiditis
   - small follicles and a few lymphocytes
2. post-radiation fibrosis
   - after 131- I treatment

Question 9

Thyroid adenoma

Answer 9

• most common thyroid neoplasm, benign
• gross: solitary, encapsulated. May be cystic
• microscopic: fibrous encapsulation without invasion, uniform pattern of cells within nodule, peripheral compression b the nodule (pushing margin), absence of additional nodule in thyroid

Question 10

Papillary carcinoma of thyroid

Answer 10

• most common thyroid Ca
• prior radiation to neck
• RET/PTC oncogene
• indolent growth
• microscopic: papillary fronds, Orphan Annie eyes (follicles of epithelial cells with large vesicular nucleus that appears empty),
• FNA: papillary groups, psammoma bodies, nuclei with grooves, intranuclear cytoplasmic inclusions (pseudo)
• can have follicular variant

Question 11

Follicular Ca of thyroid gland

Answer 11

• gross: solitary, solid, tan, gray-white, fleshy
• RAS mutation
• hematogenous spread
• microscopic: encapsulated or grossly invasive
• evidence of malignancy: capsular invasion, vascular invasion, distant metastasis

Question 12

Hurthle cell carcinoma

Answer 12

• rare
• variant of follicular carcinoma
• individuall cells are uniformly eosinophilic due to abundant mitochondria

Question 13

Medullary Carcinoma of thyroid

Answer 13

• 5-15% of thyroid cancers
• parafollicular cell (C cell) tumor
• may be familial
• may be part of MEN type IIA and IIB syndrome
• RET mutation
• gross: non encapsulated, solid, hello white, often bilateral-microscopic: small uniform round or spindle cells in nests or sheets. Surrounding dense fibrous stroma with amyloid
• calcitonin production

Question 14

Undifferentiated anapestic carcinoma of thyroid

Answer 14

• most agressive
• survival only months
• rare
• elderly, women
• large bulky mass “bull neck appearance”
• p53 mutation
• rapidly growing
• microscopic: ugly cells-large multinucleate, small or spindled cells, no follicular or papillary growth patterns