Thyroid pathology Flashcards
Describe the path of descent the thyroid goes through in embryological developmment
Develops from invagination of pharyngeal epithelium.
Descends from the foramen caecum to the normal place at the thyroglossal duct.
Failure to descend in embryological development
Lingual thyroid
Excessive descent in embryological development
Located retrosternally in mediastinum
Parafollicular cells are also known as
C cells
Histological appearance of parafollicular cells
Larger cells (than follicular cells) that have clear cytoplasm.
Where does TSH act on the thyroid?
Thyroid follicular epithelium.
Histological appearence of a colloid
Big pink circles (the biggest cells in the thyroid) surrounded by small follicular cells.
How would you distinguish between follicular cells and parafollicular cells on a histological slide?
Parafollicular cells have a clear cytoplasm whereas follicular cells stain pink/purple.
What issue in the pituitary can cause hyperthyroidism?
TSH secreting pituitary adenoma.
What pathology in the ovaries can cause hyperthyroidism?
Struma ovarii- rare tumour in the ovaries that is made up of thyroid tissue.
What is thyrotoxicosis? What can cause thyrotoxicosis?
Excessive release of thyroid hormones (of any cause). Causes include graves, hyperfunctioning neoplasms e.g. adenomas and carcinomas.
Triad of features associated with graves disease
Hyperthyroidism with diffuse enlargement of the thyroid
Eye changes (exopthalmos)
Pretibial myxoedema.
How do autoantibodies cause damage to the thyroid in Hashimotors?
Anti-thyroglobulin and anti-peroxidase bind to the thyroid receptors and cause antibody dependent cell mediated toxicity.
CD8+ T cells mediate destruction of the thyroid epithelium.
T cell activation causes gamma interferon (cytokine) to be realised- recruiting macrophages to the site causing damage to the thyroid follicles.
Histological findings of Hashimotors disease?
Lymphoid follicles present within the thyroid gland.
Beginning to lose thyroid follicles.
Why does a reduction in T3 and T4 production cause goitre?
Reduction in levels of T3 and T4 mean that to compensate- levels of TSH increase. This stimulates gland enlargement.
Diffuse goitre
Enlargement of the whole thyroid
Nodular goitre
Enlargement of part of the thyroid.
Causes of diffuse goitre
Ingestion of substances that limit T4/T3 production.
Inborn errors of metabolism (dysmorphogenesis)
Causes of nodular goitre
Variation of response of follicular cells to external stimuli- mutation in the TSH signalling pathway
Rupture of follicles- could be due to heamorrhage, scarring, calcification.
What types of neoplasms (new growths) can you get in the thyroid gland?
Benign- adenoma
Malignant- carcinoma
Name the types of carcinoma that can present in the thyroid gland?
Papillary carcinoma (75-80%) Follicular carcinoma (10-20% Medullary carcinoma (5%) Anaplastic carcinoma (<5%)
Name the type of adenoma that presents in the thyroid gland
Follicular adenoma
Presentation of an adenoma on the thyroid?
Discrete solitary mass.
Encapsulated by a collagen cuff.
Made up of thyroid follicle cells.
What can a follicular adenoma be difficult to distinguish from?
Follicular cell carcinoma or a dominant nodule in multinodular goitre.
Genetic association of adenomas
Some patients have mutant ras or PIK3CA
Some patients have mutations in TSHR (thyroid stimulating hormone receptor) pathway.
Who is most likely to be affected by carcinomas of the thyroid gland?
Female predominance
Predominantly occurs in early adulthood.
What environmental factors are said to make you susceptible to thyroid carcinomas?
Ionising radiation to the neck
Iodine deficiency
Presentation of papillary carcinoma
Usually solitary nodule in the thyroid. (however can be multifocal)
Often cystic
May be calcified.
Characteristics of papillary carcinoma
Predisposed to having very early lymph node involvement. (different to follicular cell carcinoma because it spreads via blood)
Typical presentation of papillary carcinoma in a patient
Patient comes in with nodule on neck. Moves when swallowing. Patient also has enlarged lymph node.
Survival rate of papillary carcinoma
10 year survival is above 95%.
Presentation of a follicular cell carcinoma
Generally a slow growing, painless, singular nodule.
It is non-functional.
May have surrounding capsule
How do follicular cell carcinomas spread and to where would they go?
They spread via the blood. Generally to the bones, liver and lungs.
They won’t spread to the lymph nodes- good way to distinguish between them and papillary carcinomas.
What differentiates a follicular cell adenoma from a follicular cell carcinoma?
For it to be a carcinoma you need capsular or vascular infiltration.
Also has more solid, and less follicular cell, architecture.
Prognosis of follicular carcinoma
Dependent on level of invasion. If it is a high stage at presentation- 10 year survival is about 50%.
Minimally invasive lesions- 90% 10 year survival
Medullary thyroid carcinoma (MTC) origin
Derived from C cells (also known as parafollicular cells).
What do MTC’s secrete?
Calcitonin.
What are MTCs associated with?
Associated with multiple endocrine neoplasia (types IIA or IIB) (multiple tumours in the endocrine system).
Familial medullary carcinoma.
Most MTC cases are?
Sporadic (70%).
Sporadic MTC cases present as
One solitary nodule
Familial cases of MTC present as
Multicentric or bicentric.
Histological description of MTC tumours
Composed of spindal or polygonal cells arranged in nests, trabeculae or follicles.
Calcitonin depositing.
Describe the characteristics of MTCs
They are aggressive tumours. Sporadic cases will show a neck mass with local effects of dysphagia, hoarseness, airway compromise.
Characteristics of anaplastic carcinomas
They are aggressive and rapidly growing tumours. They involve neck structures and are undifferentiated.
Who is likely to get an anaplastic carcinoma
Older people
People who have had another sort of thyroid cancer.
