Thyroid Pathology Flashcards
What is histology?
- Samples of solid tissue – either biopsy or resection
- Fixed in formalin, then embedded in paraffin blocks
- Cut thinly and stained with Haemotoxylin and Eosin
- Tissue architecture and cytological features well preserved
What is cytology?
- Material is sucked out of a lesion (aspirated) using a needle, fluid medium
- The material is then smeared straight onto a slide (direct preparation)
- Or centrifuged down and filtered before being applied to a slide (liquid based cytology)
- Can make a cell block (pellet of cells can be processed by histology) for ancillary testing
What are the types of benign thyroid lesions?
- Multinodular Goitre (enlarged and nodular)
- Graves Disease
- Hashimotos Thyroiditis (hypothyroidism)
- Follicular adenoma (usually singular, no invasion)
Describe multi-nodular goitre
-Most common thyroid disease
-Can cause hyperthyroidism as well as hypothyroidism
-Multilobulated asymmetrically enlarged glands
-Trying to produce more of thyroid products intermittently then involuting
=Dilated follicles (contain macrophages)
=Cholesterol clefts
=Variably sized follicles (tiny vs enlarged)
=Foamy macrophages
=Cystically dilated follicles
=Fibrous septae (in between follicles)
Describe Graves’ Disease
-Also known as toxic nodular goitre
-Autoimmune disease with antibodies to thyroid stimulating hormone receptor
-Causes hyperthyroidism (stimulates gland)
=Papillary architecture (not follicles)
=Clinical and biochemical diagnosis (not made on histology)
=Cells (follicular epithelial cells) have more columnar appearance, basally located nucleus
=Bubble appearance, scalloping colloid
Describe Hashimoto’s Thyroiditis
-Autoimmune process affecting the thyroid
-Associated with thyroglobulin and thyroid peroxidase antibodies
-Lymphoid predominant inflammation, follicular cell oncocytic change and variable degrees of gland destruction, disruption to parenchyma
=Lymphoid aggregates with germinal centre formation
=Small lymphocytes
=Oncocytic epithelial cells (looks pink)
=Fibrosis
Describe Follicular Adenoma
-Completely encapsulated lesion
-Made up of thyroid follicles
-Clonal population but benign
-If capsular or vascular invasion then becomes follicular carcinoma
=No invasion of thick fibrous capsule
=Lesion made up of small, collapsed, colloid sparse follicles
What are the types of malignant thyroid lesions?
-Follicular Carcinoma
-Papillary Carcinoma
Rare:
-Medullary Carcinoma
-Anaplastic Carcinoma
What other thyroid tumours are there?
-Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)
=looks like follicular adenoma and nucleus like papillary carcinomas, dont behave like carcinomas so benign, low metastatic rate)
-Follicular adenoma & Hürthle cell adenoma= benign tumours with pink cytoplasm by numerous mitochondria
-Hyalinizing trabecular tumour= very rare, gene translocation
-Well differentiated tumour of uncertain malignant potential (WDT-UMP)
-Follicular tumour of uncertain malignant potential (FT-UMP)
-Follicular carcinoma & Hürthle cell carcinoma
-Papillary carcinoma
-Medullary carcinoma
-Poorly differentiated carcinoma
=specific entity, intermediate prognosis with anaplastic
-Anaplastic carcinoma
-Primary thyroid lymphoma
-Metastatic disease &
-Other rare tumours
Describe follicular carcinoma
-Follicular adenoma but tumour invades through fibrous capsule, blood vessels (produced follicles)
Describe papillary carcinoma
- Papillary structures (long fingers lined by malignant cells)
- Can be encapsulated
1. Intranuclear inclusions
2. Nuclear clearing and irregularity
3. Nuclear grooves - Psammoma bodies (calcified laminated bodies)
- Follicular variant (NIfTP)
Describe medullary carcinoma
- Sometimes associated with genetic conditions (multiple endocrine neoplasia)
- Looks like anything, wide range of appearance (spindle like appearance, can have nuclear inclusion and grooves/ epethioid appearance)
- Amyloid associated! Congo red stain
Describe anaplastic carcinoma
- Poor prognosis
- High grade malignancies
- Hyperchromatic
Describe thyroid cytology
- Screening test only
- Most important features is colloid
- Cell to colloid ratio is a good indicator of malignancy (less= malignant)
- Colloid is a reassuring feature (benign, as malignant less)
- For adequacy must have 6 groups of at least 10 cells
What is the Bethesda/Thy classification
(fine needle aspirate diagnoses)?
- Unsatisfactory, (not enough cells) (Thy1)
- Cyst fluid (not enough epithelium to identify histogenesis of cyst) (Thy1c)
- Non-neoplastic thyroid lesion (Thy2)
- Cyst in non-neoplastic lesion (Thy2c)
- Possible neoplasm thyroid (Thy3a)
- Probable or certain follicular neoplasm (Thy3f)- only in histology to differentiate
- Suspicion of malignant neoplasm (Thy4)
- Malignant neoplasm (Thy5)
