A 55-year-old woman presents with a pathological fracture of the femur. Biopsy of the lesion shows well-differentiated thyroid tissue with a follicular pattern. Her primary thyroid lesion was removed two years ago and showed transcapsular invasion. The predominant route by which follicular thyroid carcinoma disseminates is:

• A Lymphatic spread to cervical nodes
• B Direct contiguous extension into the trachea
• C Haematogenous spread to bone and lung ✓
• D Transcoelomic spread to the peritoneum

Explanation

Follicular thyroid characteristically spreads haematogenously, giving early bone and lung metastases, sometimes as the first manifestation, exactly as in this patient whose femoral lesion contains differentiated thyroid tissue. This contrasts sharply with papillary carcinoma, which spreads predominantly through lymphatics to cervical nodes. Because follicular lesions are distinguished from adenomas only by capsular and vascular invasion, which fine needle aspiration cannot assess, histology of the excised specimen is required for diagnosis.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.