174. Thyroid Histology/Pathology Flashcards by Michael Peabody

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)

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Integrity of the ___ is important in determining malignant potential of follicular adenoma

tumor capsule

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From cytology (FNA):

repetitive pattern of microfollicles and rosettes
single cell type, scant colloid

Follicular/Hurthle Cell Neoplasm

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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

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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

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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

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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)

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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)

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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

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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

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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

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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

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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)

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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

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Multiple cycles of hyperplasia and involution lead to..

Nodularity

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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

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Graves’ Disease

Descent/maturation to adult shape for the thyroid completed in week __ of gestation

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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

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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

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Histology of thyroid

Histology:
Lined by cuboidal or squamous epithelium

Contains proteinaceous fluid

Follicles may or may not be present

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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

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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

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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

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Follicular/Hurthle Cell Adenoma

When should a thyroid nodule be biopsied?

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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)

174. Thyroid Histology/Pathology Flashcards

(39 cards)