Thyroid nodules and thyroid cancer

Question 1

What is the function of normal proto-oncogenes RET and BRAF ?

Answer 1

To promote cell growth and proliferation.

Question 2

What is the normal function of the tumour supressor gene p53 ?

Answer 2

They slow down cell division and induce apoptosis, if the cells divide uncontrollably.

Question 3

What are thyroid adenomas ?

Answer 3

These are benign cold non-functional thyroid nodules. On histology they are follicular cells with no capsules or vascular invasions.

Question 4

What is differentiated thyroid cancer ?

Answer 4

These are cancers that arise from follicular cells.

Question 5

What are the two types of differentiated thyroid cancer ?

Answer 5

Papillary carcinoma and Follicular carcinoma.

Question 6

What is the most common thyroid cancer ?

Answer 6

Papillary carcinoma that develops due to mutations in BRAF gene and RET/PTC rearrangement. Childhood exposure to ionising radiation is a risk factor. However, it has excellent prognosis.

Question 7

What are the histological hallmark of papillary thyroid carcinoma ?

Answer 7

1) Orphan Annie eye appearance due to fewer proteins and low amount of DNA in the nucleus.
2) Psammoma bodies which are calcium deposits in papillae.

Question 8

What is the cause of follicular thyroid carcinoma ?

Answer 8

follicular carcinoma is caused by activation of RAS oncogene and PAX-8 and PPAR-gamma translocation which promotes follicular cell proliferation. It has a good prognosis. however, it can break through fibrous capsule and spread to the other parts of the body.

Question 9

What are medullary thyroid carcinomas ?

Answer 9

These cancers arise from the parafollicular cells or C cells due to a single mutation in RET oncogene and is usually a single carcinoma in one lobe of the thyroid. It is often associated with MEN type 2a and 2b.

Question 10

What is the histology of medullary thyroid carcinoma ?

Answer 10

These are spindle shaped cells with amyloid deposit which can be visualised using congo red stain.

Question 11

What are anaplastic thyroid carcinoma ?

Answer 11

Anaplastic thyroid carcinoma is caused by TP-53 tumour suppressor gene. It is a rare cancer seen typically in older individuals and has a poor prognosis. They can arise from papillary or follicular cancers and grow beyond the fibrous capsule.

Question 12

What are the signs and symptoms of thyroid cancer ?

Answer 12

• The first sign is a solitary painless nodule.
• Hard and immovable nodules are more likely to be tumours.
• If the tumour is too big it can cause hoarseness and dysphagia.
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Question 13

What differentiate hot thyroid nodule from thyroid cancer ?

Answer 13

Thyroid cancers are non-functional nodules that do not secrete any hormones.

Question 14

Calcitonin levels are usually elevated in ______ thyroid carcinoma ?

Answer 14

Medullary thyroid carcinoma that arise from the C-Cells.

Question 15

What is the cause of post thyroidectomy hoarseness ?

Answer 15

Damage to the right recurrent laryngeal nerve that innervate most of the laryngeal muscles.

Question 16

What is the cause of reduced pitch of the voice following thyroidectomy ?

Answer 16

Damage to the external branch of the superior laryngeal nerve which innervates the innervates the cricothyroid muscle.