Anaplastic thyroid cancer

Sub-section: Thyroid Section: Endocrine

Incidence

• Approximately 1% of all thyroid malignancies
• Most aggressive form of Thyroid Ca
• Disease-specific mortality ~ 100%

Clinical

• Typically an older patient with dysphagia, cervical tenderness, and a painful, rapidly enlarging neck mass
• Often have a history of prior or coexistent Differentiated thyroid cancer
• Up to 50% have history of goitre
• Clinical findings may also include SVC syndrome
• Clinical situation deteriorates rapidly into tracheal obstruction and rapid local invasion of surrounding structures

Pathology

• Macroscopic
  • Locally invasive, with a firm, whitish appearance
• Microscopic
  • Giant cells with intranuclear cytoplasmic invaginations
  • Cell types range from moderately differentiated to extremely poorly differentiated cells.
  • Three types of cell populations have been classified:
    • Small spindle cell
    • Giant cell
    • Squamous
    • All have a poor prognosis
  • p53 mutations are found in 15% of tumours, a much higher rate than DTCs
  • Occasionally, squamous cell elements or islands of more recognizable DTC, such as PTC, can be identified within the locus of the tumour
  • Finding led to speculation that ATC might arise from more differentiated carcinoma – No solid proof of this theory

Management

• Overview

  • Results of any surgical treatment tempered by its rapidly progressive clinical course
  • Distant spread is present in 90% of patients at the time of diagnosis
    • Most commonly to the lungs
  • Most reports of resection are not optimistic
    • FNA is accurate in 90% of cases, making open biopsy an uncommon surgical indication
    • Small improvement in survival may be seen after resection (if appropriate)

• Because the prognosis is so grim, end-of-life planning and consideration of palliation must be part of early management and counselling

• By stage

  • Small incidental finding
    • Total thyroidectomy and adjuvant chemotherapy or radiotherapy should be considered
  • Resectable locoregional disease
    • Total thyroidectomy + lymphadenectomy + adjuvant chemotherapy and radiotherapy.
    • Post-op external-beam irradiation or adjunctive chemotherapy adds little to the overall prognosis (but should be considered)
  • Unresectable disease
    • Radiotherapy and chemotherapy can be considered.
    • Should consider an isthmus division.