Thyroid Pathology Flashcards
What is the agent associated with infectious thyroiditis?
Tuberculosis
Subacute (de Quervain) granulomatous thyroiditis
- Onset
- Course
- Histology
- Viral or postviral response
- Painful, self-limited disease
- Cell types
- Suppurative: Neutrophils
- Granulomatous (Giant cells)
Hashimoto’s Thyroiditis
Morphology
Histology
- Diffuse enlargement: Possible nodularity
- Lymphocytic inflammation
- Germinal centers (inflammatory follicles)
- Hurthle cell change around the lymphocytes
Fibrosing thyroiditis
Morphology
Histology
- Hard and fixed thyroid, painless
- Dense fibrosis – Collagen fibers
- Fibrosis can extend outside of thyroid
Graves’ Disease Histology
Irregular follicles and scalloped colloid
Goiter Histology
- Follicles lined by crowded columnar cells
- Variably sized follicles
- Abundant colloid
- Initial stages
- Symmetrical, diffuse enlargement
- Recurrent episodes lead to a multinodular gland
- With time will develop changes
- Cysts, fibrosis, calcification, hemorrhage
Solitary Palpable Thyroid Nodule Epidemiology
- Incidence in US: 1-10%
- F:M = 4:1
- Majority are non-neoplastic (focal hyperplasia, simple cysts) or benign (adenoma)
- Carcinoma relatively uncommon (<1% of all solitary thyroid nodules)
What are fine needle aspirates?
What are the benefits?
What are they diagnostic for?
What can they not diagnose?
- Useful initial approach for diagnosis of nodule
- Quick, inexpensive, minimal complications
- Diagnostic for papillary carcinoma, medullary carcinoma, lymphoma and metastatic tumors
- Cannot differentiate follicular adenoma from follicular adenoma from follicular carcinoma or from hyperplastic nodules
Follicular Adenoma
Morphology?
Functional?
Transformation risk?
Thyrotoxicosis?
- Various morphologic appearances – Not clinically significant
- Most are nonfunctional
- Do not transform to carcinoma
- Functional adenomas produce thyrotoxicosis
Follicular Adenoma
Cellular Characteristics
- Solitary nodule
- Complete fibrous encapsulation
- No capsular or vascular invasion
- Different growth pattern from adjacent normal gland
Thyroid carcinoma
Epidemiology
Biggest Risk Factor
- Uncommon, low mortality
- F > M
- All ages including children
- Most significant proven risk factor is ionizing radiation
Thyroid Carcinoma
Genetics (Mutation, Chromosomal Abnormalities, Fusion Gene)
Papilarry CA
Relative prevalence
Epidemiology
Prognosis
Metastatic route
- (85%-95%)
- Younger age group (20s-40s), women
- Excellent prognosis (>95% survival at 20 years)
Adverse prognostic factors include: Age > 40, Tumor > 5 cm, Extrathyroidal extension, Osseous metastasis - Preferentially metastasize by way of lymphatics
Cervical nodes involved in up to 50% of cases)
Papillary CA Histology
What are the most important features?
-
Nuclear features most important
- Clear nuclei “Orphan Annie eyes”
- Intranuclear cytoplasmic inclusions
- Intranuclear grooves
- Papillary architecture (Variants may be different)
- “Chewing gum” colloid
- Psammoma bodies
- Multinucleated giant bodies
Follicular CA
Relative prevalence
Epidemiology
Presentation
Prognosis
Metastatic route
- 5%
- Present at older age than papillary
- Slowly enlarging painless nodule
- Prognosis depends on stage and extent of invasion
- Vascular spread to bone, lungs, liver, etc
Follicular CA
Role of histology for diagnostics
Criteria for malginancy
Distinguishing from follicular adenoma
- No cytologic features, typically “well-differentiated”
- Malignancy requires either:
- Capsular invasion
- Vascular invasion
- Minimally invasive carcinomas are difficult to distinguish from follicular adenomas and extensive sampling of the capsule is required
Papillary vs Follicular CA
Architecture
Diagnostic criteria
Psammoma bodies
Age at presentation
Focality
Predisposing factors
Metastatic spread
Prognosis
Medullary CA
Relative prevalence
Cell lineage
Origin
Prognosis
- CA (5%)
- Neuroendocrine tumors derived from parafollicular (C-cells) of the thyroid
Calcitonin secreting - 80% are sporadic - 40s and 50s
20% with MEN-2 - Childhood - Px: 40-60% survival at 10 years
Medullary CA
Histology
Immunochemistry
- Nests of NE cells, amyloid stroma
- Calcitonin, chromogranin, synaptophysin, CEA, Keratin positive
Thyroglobulin negative
Anaplastic CA
Relative prevalence
Origin and stage
Age
History
Spread
Prognosis
- Undifferentiated tumors of follicular epithelium:
- No staining with thyroid specific immunostains
- Mean age: 65 yo
- History of long-standing goiter, differentiated thyroid carcinoma, concurrent papillary carcinoma
- Spread: Extrathyroidal spread or distant metastasis at presentation
- Causes presentation of hoarseness and neck pain
- Mortality rate is virtually 100%
- Mean survival is 6 months
Anaplastic CA
Histology
- Variable cell types:
- Spindle cells
- Epithelioid cells
- Giant cells
- Cells are pleomorphic
Other thyroid carcinomas and relative prevalences
- Lymphomas (<1%)
- Sarcomas (<1%)
