Thyroid cancer Flashcards
Does thyroid cancer cause thyrotoxicosis?
No, patients are usually euthyroid.
What are the risk factors for thyroid cancer?
- head and neck irradiation → papillary carcinomas
- female sex
- FH of thyroid cancer
What are the 4 types of thyroid cancer?
- Papillary - 80% - usually well differentiated; lymph node spread; Psammoma bodies
- Follicular - 10% - direct heamatogenous invasion; late aggressive; Hurthle cell is a sub-type
- Medullary - 4% - starts in parafollicular C cells; occurs in sporadic and familial forms; one quarter of cases are familial e.g MEN related.
- Anaplastic - undifferentiated form with vascular invasion
Lymphoma - generally B cell non-Hodgkin’s lymphoma; arises in setting of Hashimoto’s thyroiditis.
What is the aetiology of thyroid cancer?
- Causes:
- sporadic
- familial
- MEN 2A and 2B → medullary thyroid cancer
This is RARE but can be devastating
It is a cancer of the C-cells of the thyroid gland (these produce calcitonin so if too much then may be MCC)
Where do thyroid cancers spread to?
Papillary spread to local lymph nodes
Follicular/Hurthle cells spread haematogenously
What characteristics suggest that a thyroid nodule may be neoplastic rather then benign?
- Solitary not multiple
- Solid not cystic
- Younger patient
- Male
- Cold nodule - no uptake of iodine
What are the signs and symptoms of thyroid cancer?
- Palpable thyroid nodule
- Uncommon: hoarseness, dyspnoea, dysphagia(oesophageal pressure), tracheal deviation, cervical lymphadenopathy, rapid neck enlargement(lymphoma)
What investigations would you do for thyroid cancer?
Diagnosis by FNA and histology
Other:
- TSH, T3/T4 - normal
- US neck +/- FNA- nodule number/characteristics. FNA shows which type.
- Laryngoscopy - paralysed vocal cord is highly suggestive of malignancy
- I-123 thyroid scan and uptake - most cancers are cold nodules.
- Serum calcitonin - high in medullary cancer
- Genetic testing for familial syndrome - may detect RET proto-oncogene mutations found in MEN type IIA, type IIB and isolated familial medullary thyroid cancer
What % of thyroid nodules are carcinomas?
<1% - uncommon in general
How common is thyroid cancer?
- Most common endocrinological malignancy
- Rising over the decades
- F>M
- Usually diagnosed around 50yrs
- 70-80% asymptomatic
How is thyroid cancer managed?
- Total thyroidectomy ± radioiodine
- Supraphysiological doses of thyroxine (to lower the TSH levels so that TSH does NOT stimulate any remaining thyroid cancer cells, as many of these tumours cells are sensitive to TSH and may grow again)
- Measure TG (thyroglobulin) to monitor if the cancer ever returns (as everything has been wiped out so no TG should be released)
*TG is a protein produced by RER in thymocytes
What are the complications and prognosis of thyroid cancer?
- Airway obstruction
- Hypoparathyroidism
- Recurrent laryngeal nerve damage
- Bleeding
- TSH suppression AF
- radioiodine secondary tumours - these patients are at increased risk of developing acute myeloid leukaemia (AML) and chronic myeloid leukaemia
Prognosis -
- Papillary has an average 10-year survival >90%. Recurrence and metastasis is rare after surgery.
- Follicular carcinoma has a slightly worse prognosis with systemic metastasis. Hurthle cell has worst prognosis with 10-year survival of about 70%.
How do you monitor for return of thyroid cancer after thyroidectomy?
Tg should be zero as there is no thyroid tissue left. However, the value for Tg can only be trusted if anti-Tg Abs are 0. Otherwise these antibodies interact with the assay.
How does papillary thyroid cancer present?
Patient of any age
Painless neck mass +/- metastases to cervical nodes
Metastasise to lung, bone, liver
What is a major risk factor for papillary thyroid cancer?
radiation exposure
When do follicular carcinomas usually present?
Peak incidence in middle age
What is Berry’s sign in follicular carcinoma?
Malignant thyromegaly causing an absent carotid pulse
Why is FNA seldom useful for follicular thyroid cancer?
The cancer is macroscopically encapsulated
So needs hemithyroidectomy
When does a follicular adenoma become a carcinoma?
Once there is capsular invasion
What are the complications of anaplastic carcinoma?
Highly aggressive, rapidly enlarging neck mass
Anaplastic transformation of papillary, follicular or Hurthle cell carcinoma
Local invasion -→ hoarseness, dysphagia, dyspnoea
Who is most affected by anaplastic carcinoma?
Elderly females
How do anaplastic carcinomas present and what is their prognosis?
Elderly patients
Metastases common
Histology - Polymorphic, undifferentiated follicular cells, infiltration, necrotic background
Prognosis poor: most die within 1yr of diagnosis due to LOCAL invasion.
What is the origin of medullary carcinoma?
Derived from parafollicular cells (C cells)
Neural crest origin not thyroid
What is the % of cases of medullary thryoid cancer which are familial?
20% e.g. MEN
What is seen on histology in medullary thyroid cancer?
Amyloid deposition
How do you monitor for recurrence of medullary thyroid cancer?
Monitor:
- Calcitonin
- CEA
What do parafollicular C cells do?
Synthesise calcitonin for promoting calcium absorption by the skeletal system
What are the histological features of the different types of thyroid cancer?
- Papillary - optically clear nuclei, intranuclear inclusions, “Orphan Annie” eyes and psammoma bodies
- Follicular - well-demarcated, minimally invasive, hypercellular, microfollicles, absence of colloid
- Medullary - eosinophilic cells arranged in nests or sheets separated by amyloid and vascular strome; +ve for calcitonin
- Anaplastic - wide variations in appearance, spindle cell pattern, pleomorphic ginat cell pattern
