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
