1. Thyroid Malignancy
Aetiology
-Mohammed Shujauddin

2. Introduction
• Thureoeides (Ancient Greek), meaning ‘Sheild
Shaped’.
• Anterior aspect of neck.
• Two lobes connected by isthmus.
• Endocrine gland.
• Regulates BMR, stimulates somatic and psychic
growth, calcium metabolism.

3. Embryology
• Floor of primitive pharynx, caudal to tuberculum
impar. (Marked by foramen caecum of tongue)
• Median endodermal thyroid diverticulum
• Downward growth, bifurcates and forms lobes.

6. Anatomy
• Weight: About 25g (Larger in Females).
• Lies against C5, C6, C7 and T1 vertebrae.
• Lobes: Middle of thyroid cartilage to IV or V tracheal
ring.
• Isthmus: II – IV tracheal ring.
• Dimensions (cm): Lobe – 5 × 2.5 × 2.5
Isthmus – 1.2 × 1.2

7. Capsules of Thyroid
• True capsule: condensed peripheral connective
tissue of the gland.
• False capsule: derived from pretracheal layer of
deep cervical fascia. (Ligament of Berry)

8. Relation to surrounding structures

9. Blood supply
• Arterial supply:
– Superior thyroid artery (ECA)
– Inferior thyroid artery (thyrocervical trunk, SCA)
– Thyroidea ima artery (Brachiocephalic trunk or AOA)
– Accessory thyroid arteries.
• Venous drainage:
– Superior thyroid vein – IJV
– Middle thyroid vein – IJV
– Inferior thyroid vein – left bracheocephalic vein
– Fourth thyroid vein of Kocher – IJV.

11. Histology
Two types of secretory cells.
• Follicular cells:
– Columnar in active phase, cuboidal in resting phase.
– Secrete T3, T4.
– Follicles contain colloid in lumen
• Parafollicular cells (C cells):
– Fewer, lie in between follicles.
– Secrete thyrocalcitonin

12. Classification (Dunhill)
• Differentiated – 80%
– Papillary carcinoma (60%)
– Follicular carcinoma (17%)
– Paillofollicular carcinoma
– Hurthle cell carcinoma
• Undifferentiated – (20%)
– Anaplastic carcinoma (13%)
• Medullary carcinoma (6%)
• Malignant Lymphoma - (4%)
• Secondaries in thyroid (rare)

13. Etiology
• Radiation : Proloned exposure to high dose of external
radiation or radioiodine. Children and young adults.
(papillary carcinoma)
• Iodine excess and TSH
– Papillary thyroid carcinoma:•
•
•
•
External radiation or radioactive iodine therapy
Iodine sufficient areas.
Common in children and females.
RET overexpression (chr 10)
– 20% cases
– Tyrosine kinase receptor targeted by tumor promoting factors
• NTRK1 rearrangement
• Elevated TSH , Hormone dependent tumor.
• Hushimotos thyroiditis

14. – Follicular thyroid carcinoma:- agressive
• Common in females
• Iodine-deficient areas
• 50% cases with RAS oncogene mutation
• Gene translocation:- PAX- 8 and PPARγ-1
• De novo or Pre-existing Multinodular goitre
Hurthle cell carcinoma:variant of follicular thyroid carcinoma.
Abundant oxyphill cells
Spread more commonly to regional lymph nodes.
Vascular or capsular invasion.
– Medullary thyroid carcinoma:
• Origin:- parafollicular C-cells.
• Site:- Superolaterally in the thyroid lobes.
• RET gene mutation, familial and sporadic
• Associated with MEN II syndrome and pheochromocytoma with
hypertention. MCT associated with MEN II B with pheochromocytoma
(Sipple’s disease) is most aggressive.
• Not TSH dependant and does not take up radioactive iodine.

15. – Anaplastic thyroid carcinoma:- very aggressive
• Common in women 7th to 8th decade of life.
• Undifferentiated.
• Origin- dedifferentiation of differentiated PTC or FTC, or
Inactivating point mutation in p53 gene.
– Malignant Lymphoma
• NHL type
• Occurs in pre-existing Hushimoto’s thyroiditis

16. Features
Papillary
Carcinoma
Follicular
Carcinoma
Medullary
Anaplastic
Carcinoma
Frequency
60%
17%
6%
13%
Age
all ages
Middle to old
age
Middle to old
age; Familial
Old age
Female/
male ratio
2:1
3:1
1:1
1.5:1
Relation
to
radiation
Maximum
Present
None
Present
Genetic
alterations
RET gene
over
expression
RAS mutation
RET mutation
P53 loss
Cell of
origin
Follicular
Follicular
Parafollicular
Follicular
Contrasting features