Undifferentiated and aggressive tumours derived from follicular epithelium

Aetiology

• Can arise de novo or be due to dedifferentiation of another carcinoma
• Usually older patients
• Similar genetic features to papillary carcinomas and follicular carcinomas as well as p53 and β-catenin mutations

Pathophysiology

• May occur in people with a history of differentiated thyroid cancer
• Rapid growth and involvement of neck structures and death

Clinical features

• Thyroid nodule
• Features of local infiltration/compression
• Cervical lymphadenopathy
• Signs of distant metastases

Investigations

• Bloods: TSH
• Ultrasound scan
• US-FNA or biopsy: to confirm

Management

• Total thyroidectomy if resectable +/- adjuvant radiochemotherapy as needed
• Do not respond to RAI