174. Thyroid Histology/Pathology Flashcards
Gross:
- varies considerably depending on the presence and degree of fibrosis, encapsulation, and cystic change
- often a multifocal process
- microcarcinoma is < 1.0 cm
Surgery:
- near total thyroidectomy
Papillary carcinoma (PTC)
Integrity of the ___ is important in determining malignant potential of follicular adenoma
tumor capsule
From cytology (FNA):
- repetitive pattern of microfollicles and rosettes
- single cell type, scant colloid
Follicular/Hurthle Cell Neoplasm
As the thyroid descends anterior to the pharyngeal gut it is connected to the tongue by the __ which normally obliterates in week 7-10
Thyroglossal duct
Histology:
- high-grade carcinomas with no obvious follicular differentiation by histology or immunohistochemistry
- variety of morphologic patterns
- extreme cellular/nuclear pleomorphism, necrosis
Management:
- mainly palliative
Anaplastic Carcinoma
Gross:
- typically discrete, solitary, non-functional masses derived from follicular epithelium
Clinically difficult to distinguish from dominant nodules in a hyperplastic gland and it is usually impossible to predict which ones are follicular carcinomas until they are excised
Comprise about 5-10% of thyroid nodules
Follicular/Hurthle Cell Adenoma
Gross:
- Diffusely enlarged gland, solitary nodule presentation seen in more cases
Histology:
- Extensive infiltration of parenchyma by small lymphocytes/plasma cells with germinal centers
- Follicles atrophic, lined by regenerating Hurthle cells
- –> metaplastic response to the normally low cuboidal epithelium to ongoing injury
Cytology (FNA):
- Hurthle cells + a heterogeneous population of lymphoid cells
Hashimoto’s thyroiditis (Chronic lymphocytic thyroiditis)
Gross:
- Non-encapsulated, bu border can sometimes be circumscribed
- Arise from the junction of the middle and upper thirds of the thyroid lobes
Sporadic - solitary nodule
Familial - bilateral and multicentricity
Surgery:
- total thyroidectomy with lymph node dissection
Medullary Carcinoma (MTC)
Rare
Common sites: Kidney, lung, breast
Whenever pattern is “alien” think about this and anaplastic carcinoma
Very poorly differentiated tumors may be virtually impossible to distinguish morphologically from anaplastic carcinoma
Metastatic tumors
Non-invasive follicular thyroid neoplasm with papillary-like nuclear features
Encapsulated follicular variant of PFT
Clinically and genetically behaves more like a follicular neoplasm
NIFTP
Autoimmune destruction of the gland caused by circulating Abs against thyroglobulin and thyroid peroxidase (TPO)
Most common in 45-65 year olds
- female
Increased risk for developing:
- other autoimmune diseases
- B-cell non-Hodgkin lymphomas (MALT lymphomas)
- Papillary thyroid carcinoma
Hashimoto’s thyroiditis
Spectrum of changes:
- Hyperplastic stage: follicle lumen small, scant colloid, tall columnar epithelium, some papillae
- Degenerative changes: fibrosis, hemorrhage, regeneration/repair, dystrophic calcification
- Involutional stage: follicles distended w/ colloid, lined by small cuboidal/flat epithelium
Adenomatous (colloid or hyperplastic) nodules
Histology:
- variable: composed of polygonal to spindle-shaped cells, which form nests, trabeculae, and follicles
- Acellular amyloid deposits derived from altered calcitonin polypeptides are seen in adjacent stroma
- calcitonin stain positive in tumor cell and the stromal amyloid
- familial has multicentric C-cell hyperplasia
Medullary Carcinoma (MTC)
An enlarged intrathyroidal parathyroid
Clear fluid drawn on FNA
- difficult to distinguish from follicular cells
Can do immunostains for TTF/PTH or send FNA for biochemical PTH assay
Use sestamibi scan to highlight
Parathyroid cyst/adenoma
Multiple cycles of hyperplasia and involution lead to..
Nodularity
Most common cause of endogenous hyperthyroidism
Caused by breakdown in self-tolerance to thyroid autoantigens, most importantly TSH receptor
Peaks b/w 20-40 years old
Classic triad:
- hyperplasia of gland
- ophthalmopathy
- dermatopathy
Treated w/ thioamides or I-131
Graves’ Disease
Descent/maturation to adult shape for the thyroid completed in week __ of gestation
Week 7
Technique for acquiring diagnostic material in which a small, thin needle is used to remove cells from a lesion or mass in the body
First line test for investigation of most thyroid nodules
Advantages:
- simple
- safe
- accurate
- inexpensive
Fine Needle Aspiration (FNA) biopsy
Inner true capsule, which forms numerous septae, that divide the gland into lobes and lobules
Lobules are composed of 20-40 follicles, the structural units of the gland, which consist of a layer of simple epithelium enclosing a colloid-filled cavity
Histology of thyroid
Histology:
Lined by cuboidal or squamous epithelium
Contains proteinaceous fluid
Follicles may or may not be present
Thyroglossal duct cyst
Gross:
- Thyroid is diffusely and symmetrically enlarged
Histology:
- Papillary hyperplasia with tall follicular cells (secreting colloid) is a common finding
- –> can cause confusion with PTC
- benign diffusely seen papillae are broad based, short stubby, and lack nuclear features of papillary carcinoma
Graves’ Disease
Thyroid cancers without an obvious follicular or papillary pattern
- implies lack of differentiation
Correlate with nests (insulae) on histology
May find follicular or papillary areas on the same slide
Poorly Differentiated Carcinomas
Histology:
- characteristically exhibit uniformly sized follicles
- surround fibrous capsule
- compression of adjacent follicles
Capsule is usually thin, uniform, and completely intact
Surgically remove lobe
Follicular/Hurthle Cell Adenoma
When should a thyroid nodule be biopsied?
When the size of the nodule is large and US results reveal something concerning
Epithelial cells with abundant granular cytoplasm that is rich with mitochondria
Hurthle cells
Functional unit of the thyroid
Follicle containing colloid
Hallmark diagnostic feature is atypical nuclear morphology
Hypochromasia Nuclear grooves Intranuclear inclusions Ovoid nucleus Micronucleolus
Papillary carcinoma (PTC)
Genetic changes found in Follicular/Hurthle Cell carcinoma (2 of them)
RAS mutations
PAX8-PPARG fusion gene
Thyroid starts developing on what gestational day
Day 24
Where the thyroglobulin and iodide are stored so that follicular epithelial cells can use them to produce thyroid hormones
Colloid
Where does the thyroid derive from embryologically?
Endodermal
1st pharyngeal arch
Neuroendocrine neoplasms derived from C cells
- 5% of thyroid neoplasms
75% arise sporadically
Remainder occur in the setting of MEN2A or MEN2B or FMTC
Serum calcitonin and CEA are important markers
Medullary Thyroid Carcinoma (MTC)
70-75% of thyroid nodules are..
Vast majority of thyroid nodyles are non-neoplastic (benign)
Hyperplastic
Approximately 5-10% of all thyroid nodules
- 85% of all thyroid malignancies
Young age (20-40yo)
Associated w/ radiation
Nonfunctional
Can present initially as cervical lymph node metastasis
Great prognosis unless metastasis to lymph nodes
Associated w/ activation of MAP Kinase pathway
- RET rearrangements
- activating point mutations in BRAF in 30%
Papillary carcinoma (PTC)
Most common clinically significant congenital anomaly
Abnormal persistence of the thyroglossal duct
- doesn’t obliterate in weeks 7-10
Midline, spherical cystic mass, closely associated with hyoid bone
- moves with swallowing
Thyroglossal duct cyst
Malignancy in a follicular neoplasm is determined by: (2 things)
Capsular invasion
Vascular invasion
Removal of a thyroglossal duct cyst where the mid portion of the hyoid bone is also removed
Sistrunk procedure
Primary or more common secondary in thyroid
Predominantly Non-Hodgkins, B-cell type
75% associated w/ Hashimoto’s
Low grade (MALT) difficult to distinguish from CLT - obtain flow cytometry
High grade mimics anaplastic carcinoma clinically
Thyroid lymphoma
Rare <5% of thyroid tumors
Most undifferentiated carcinomas present with extensive local extension beyond thyroid
Mimics other tumors, including metastasis
Diagnosis:
- classical clinical history
- stains by pathology to exclude metastasis
- may see a concurrent well differentiated component (but not always)
Anaplastic carcinoma (undifferentiated)
