Thyroid Malignancies
Overview
Thyroid carcinomas arise from either the follicular epithelium (papillary, follicular, anaplastic types) or the parafollicular C-cells (medullary type). They commonly present as a painless, firm, solitary nodule that is 'cold' on Tc-99m pertechnetate scintigraphy.
Key Pathological Types
- Papillary Carcinoma (~80%): Best prognosis. Linked to childhood radiation exposure. Microscopy: papillary architecture, 'Orphan Annie eye' optically clear nuclei, nuclear grooves, Psammoma bodies (concentric calcifications). Spreads via cervical lymphatics.
- Follicular Carcinoma (~10-15%): Linked to dietary iodine deficiency. FNAC cannot diagnose it — capsular or vascular invasion is required on histology. Spreads haematogenously to bone and lung.
- Medullary Carcinoma (~5%): From parafollicular C-cells. Secretes calcitonin (tumour marker). Associated with MEN 2A and MEN 2B. Amyloid stroma on histology.
- Anaplastic Carcinoma (<5%): Elderly patients, rapidly fatal. Invades trachea, oesophagus, and recurrent laryngeal nerve. Presents with acute dyspnoea and dysphagia.
Suspicious Ultrasound Features
- Hypoechoic solid nodule, taller than wide.
- Irregular / spiculated margins.
- Microcalcifications (psammoma bodies in papillary).
- Central vascularity (Doppler) rather than peripheral.
- Abnormal ipsilateral cervical lymph nodes.
WarningFollicular Carcinoma: The FNAC Trap
A follicular adenoma and follicular carcinoma are cytologically IDENTICAL on FNAC. The diagnosis of carcinoma requires histological capsular or vascular invasion on the surgical specimen. This is why all 'follicular neoplasms' (Thy3/Bethesda IV) mandate surgical hemithyroidectomy.
High Yield Facts
LightbulbFRCR / MD Prep Pearl
Papillary and follicular cancers are 'differentiated' and retain some iodine uptake — amenable to Radio-iodine (I-131) therapy. Medullary and anaplastic cancers do NOT uptake iodine. Serum thyroglobulin is the post-thyroidectomy tumour marker for differentiated thyroid cancer recurrence.