Medullary Thyroid Carcinoma Surgical Extent
A 44-year-old man has a two month anterior neck swelling. A hard 1.5 cm lump in the left lobe moves with swallowing, and no cervical lymph nodes are palpable. Ultrasound shows a mildly enlarged thyroid with a 1.5 cm solid left lobe nodule and a normal right lobe. Fine needle aspiration confirms medullary thyroid carcinoma. Which of the following is the most appropriate procedure?
- A.Enucleation of the nodule
- B.Total thyroidectomyCorrect
- C.Left hemithyroidectomy
- D.Subtotal thyroidectomy
Explanation
Medullary thyroid carcinoma arises from parafollicular C cells, which are distributed throughout both thyroid lobes, and this biology dictates a more aggressive operation than for papillary or follicular cancer. Even when imaging shows a single nodule, medullary carcinoma is frequently multifocal and bilateral, particularly in hereditary cases linked to RET proto oncogene mutations and the MEN 2 syndromes. It also metastasises early to central and lateral compartment lymph nodes, so total thyroidectomy with central neck dissection is the standard operation and lesser resections are inadequate. Unlike differentiated thyroid cancer, medullary carcinoma does not concentrate iodine, so radioiodine cannot treat residual disease and TSH suppression is ineffective; the first operation is therefore the main chance of cure. Preoperative work up should include serum calcitonin and carcinoembryonic antigen, plasma metanephrines or urinary catecholamines to exclude a phaeochromocytoma, and serum calcium with parathyroid hormone, plus germline RET testing. A coexisting phaeochromocytoma must always be resected before the thyroid, otherwise induction of anaesthesia may precipitate a hypertensive crisis. Postoperatively, calcitonin is the sensitive marker used to detect persistent or recurrent disease. Hemithyroidectomy, subtotal resection and enucleation all leave C cells behind and risk persistent disease.
Why each option
- A.
- Enucleation is oncologically inadequate for any thyroid malignancy and does not address nodal spread.
- B.
- Correct. Because C cells are distributed throughout the gland and disease is often multifocal, total thyroidectomy with central compartment dissection is standard.
- C.
- A unilateral resection leaves contralateral C cells and probable occult foci, and radioiodine cannot compensate for residual disease.
- D.
- Leaving a remnant of thyroid tissue leaves potentially malignant C cells and makes calcitonin follow up unreliable.
Reference: American Thyroid Association Guidelines for the Management of Medullary Thyroid Carcinoma, Thyroid, 2015
This is one of 3,009 questions in the MedBoardSA SMLE bank, with timed test mode, tutor mode, and progress tracking by topic.
Practise the full bank