SM_177b: Thyroid Histology / Pathology Flashcards
Describe embryology of the thyroid
Thyroid embryology
- Develops day 24 of gestation
- Endodermal: 1st pharyngeal arch
- Descends anterior to pharyngeal gut
- Connected to tongue by thyroglossal duct which normally obliterates in week 7-10
- Descent/maturation to adult shape completed in week 7 of gestation
Thyroid final location is ____
Thyroid final location is anterior to trachea below the Adams apple
Normal thyroid gland is ____, while thyroid nodules move with ____
Normal thyroid gland is not palpable, while thyroid nodules move with deglutition
Thyroid is composed of ____
Thyroid is composed of C-cells (parafollicular cells)
Summarize anatomy and development of the thyroid
Anatomy and development of the thyroid
- Develops early in life
- “H” shaped, located anteriorly in lower neck, closely associated with parathyroid glands
- Functional unit is a follicle containing colloid, C cells are minor component
- Moves with swallowing, normal sized gland is not palpable
Fine needle aspiration biopsy is advantageous because it is ____, ____, ____, and ____
Fine needle aspiration biopsy is advantageous because it is simple, safe, accurate, and expensive
Describe the thyroid fine needle aspiration biopsy reporting guidelines
Thyroid fine needle aspiration biopsy reporting guidelines
- First line test for investigating most thyroid nodules
- Marked female predilection for all thyroid disease
Thyroglossal duct cyst is ____
Thyroglossal duct cyst is midline spherical cystic mass closely associated with hyoid bone that moves with deglutition
- Abnormal persistence of thyroglossal duct
- Lined by cuboidal or squamous epithelium, contains proteinaceous fluid, ± follicles
- Successful surgery needs removal of mid-portion of hyoid bone (Sistrunk procedure)
Chronic lymphocytic (Hashimoto) thyroiditis is ____
Chronic lymphocytic (Hashimoto) thyroiditis is autoimmune destruction of the gland caused by circulating antibodies against thyroglobulin and thyroid peroxidase
- 45-65 years
- Female predominance
- Increased risk for other autoimmune diseases, B-cell non-Hodgkin lymphomas, papillary thyroid carcinoma
Describe pathology of chronic lymphocytic (Hashimoto) thyroiditis
Chronic lymphocytic (Hashimoto) thyroiditis pathology
- Gross: diffusely enlarged gland, solitary nodule sometimes
- Histology: excessive infiltration of parenchyma by small lymphocytes / plasma cells with germinal centers, follicles atrophic and lined by regenerating Hurthle cells
- Cytology (fine needle aspiration): Hurthle cells and heterogeneous population of lymphoid cells
Hurthle cells are ____ and are seen in ____
Hurthle cells are a metaplastic response of normally low cuboidal epithelium to ongoing injury and are seen in chronic lymphocytic (Hashimoto) thyroiditis
Graves disease is the most common cause of ____ is caused by ____
Graves disease is the most common cause of endogenous hyperthyroidism and is caused by breakdown in self-tolerance to thyroid autoantigens (most importantly TSH receptor)
Graves disease presents with triad of ____, ____, and ____
Graves disease presents with triad of hyperplasia of thyroid gland, opthalmopathy, dermatopathy
- Peak between 20-40 years
- Treatment is radioactive iodine or drug therapy
Graves disease papillae LACK ___
Graves disease papillae LACK nuclear features of papillary carcinoma
- Gross: thyroid diffusely and symmetrically enlarged
- Papillary hyperplasia with tall follicular cells
Goiter is ___
Goiter is enlarged thyroid gland
Most thyroid nodules are ___
Most thyroid nodules are hyperplastic
Describe stages of adenomatous (colloid or hyperplastic nodules)
Stages of adenomatous (colloid or hyperplastic nodules)
- Hyperplastic: follicle lumen small, scant colloid, tall columnar epithelium, some papillae
- Degenerative changes: fibrosis, hemorrhage, regeneration / repair, dystrophic calcification
- Involutional stage: follicles distended with colloid, lined by small cuboidal / flat epithelium
Benign thyroid neoplasms are usually ____, while malignant thyroid neoplasms are usually ____
Benign thyroid neoplasms are usually adenomas, while malignant thyroid neoplasms are usually well differentiated carcinomaas (papillary, follicular)
Describe follicular / Hurthle cell adenoma
Fzollicular / Hurthle cell adenoma
- Gross: typically discrete, solitary, nonfunctional masses derived from follicular epithelium
- Clinically difficult to distinguish from dominant nodules in hyperplastic gland and usually impossible to predict which are follicular carcinomas until they are excised
Follicular / Hurthle cell adenomas exhibit ____, ____, and ____
Follicular / Hurthle cell adenomas exhibit uniformly sized follicles, surrounding fibrous capsule, and compression of adjacent follicles
____ is important for determining malignant potential
Integrity of thyroid tumor capsule is important for determining malignant potential
- Adenomas: capsule thin, uniform, completely intact
Describe cytology of follicular/Hurthle cell neoplasm
Follicular/Hurthle cell neoplasm cytology
- Repetitive pattern of microfollicles and rosettes
- Single cell type, scant colloid
- Distinction between follicular adenoma and carcinoma is not possible by fine needle aspiration
- Fine needle aspiration diagnosis: follicular neoplasm
Malignancy in follicular neoplasm is determined by ___ and ___
Malignancy in follicular neoplasm is determined by capsular invasion and vascular invasion
- Genetic changes: RAS mutations, PAX8-PPARG fusion gene
___ is the most common thryoid malignancy
Papillary carcinoma is the most common thryoid malignancy
- 20-40 years old
- Associated with radiation
- Nonfunctional
- Can present initially as cervical lymph node metastasis
- Usually great prognosis, metastasize to lymph nodes
- Associated with activation of MAP kinase pathway
Papillary carcinoma hallmark diagnostic feature is ___
Papillary carcinoma hallmark diagnostic feature is atypical nuclear morphology
Noninvasive follicular thyroid neoplasm with papillary-like nuclear features clinically sand genetically behaves like a ___
Noninvasive follicular thyroid neoplasm with papillary-like nuclear features clinically sand genetically behaves like a follicular neoplasm
- Used to describe follicular variant of PTC
Poorly differentiated carcinoma lack ___ and correlate with ___ on histology
Poorly differentiated carcinoma lack an obvious follicular or papillary pattern and correlate with insulae (nests) on histology
____ is a neuroendocrine neoplasm derived from C cells and accounts for 5% of thyroid neoplasms
Medullary carcinoma is a neuroendocrine neoplasm derived from C cells and accounts for 5% of thyroid neoplasms
- Most sporadically, remainder as MEN 2A or 2B or familial tumors
- Activating point mutations in RET proto-oncogene involved in development of familial and sporadic
- Serum calcitonin and CEA important markers for diagnosis / recurrence monitoring
Medullary carcinomas are ___ and typically arise from ___
Medullary carcinomas are non-encapsulated and typically arise from junction of middle and upper thirds of thyroid lobes (C-cells most densely dispersed)
- Histology: variable, acellular amyloid deposits, calcitonin positive, familial has multicentric C-cell hyperplasia
Anaplastic (undifferentiated) carcinomas of thyroid present with ___
Anaplastic (undifferentiated) carcinomas of thyroid present with extensive loca; extensive beyond the thyroid
- High-grade carcinomas with no obious follicular differentiation, extreme cellular / nuclear pleomorphism, necrosis
Metastatic thyroid tumors are ___
Metastatic thyroid tumors are rare
Thyroid lymphoma is often associated with ____ and predominantly ____
Thyroid lymphoma is often associated with Hashimoto’s thyroiditis and predominantly non-Hodgkins lymphoma B cell type
- Low grade (MALT): difficult to distinguish from chronic lymphocytic (Hashimoto) thyroiditis
- High grade: mimics anaplastic carcinoma
Parathyroid cyst / adenoma is ____
Parathyroid cyst / adenoma is enlarged intrathyroidal parathyroid that can be occassionally encountered as a nodule
- Difficult to distinguish from follicular cells
Thyroid enlargement nodules are ____ common in women than men
Thyroid enlargement nodules are more common in women than men
___ is most useful screening and diagnostic test for thyroid nodules
Fine needle aspiration is most useful screening and diagnostic test for thyroid nodules
Common thyroid neoplasms have ____ prognosis
Common thyroid neoplasms have good prognosis
