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SU22.1-6 | Thyroid and Parathyroid Surgery — Practice Quiz
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During a thyroidectomy the surgeon takes care near the superior thyroid pole. Which nerve is most closely related to the superior thyroid artery at this point, and what is the consequence of its injury?
Correct. The external (superior) laryngeal nerve runs with the superior thyroid artery near the upper pole; injury weakens the cricothyroid and causes loss of high pitch and voice fatigue (the classic 'opera singer' nerve).
Superior pole/superior thyroid artery = external laryngeal nerve (pitch); inferior thyroid artery = recurrent laryngeal nerve.
At the superior pole the external laryngeal nerve accompanies the superior thyroid artery; the recurrent laryngeal nerve relates to the inferior thyroid artery near the lower pole.
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A 30-year-old woman has a lump in the lower anterior neck. Which physical sign best confirms that the swelling arises from the thyroid gland rather than another neck structure?
Correct. A thyroid swelling moves up on swallowing because the gland is tethered to the larynx by the pretracheal fascia. Movement on tongue protrusion is the hallmark of a thyroglossal cyst.
Thyroid swelling moves on swallowing; thyroglossal cyst also moves on tongue protrusion.
Movement on swallowing (pretracheal fascia tethering) localises a swelling to the thyroid; movement on tongue protrusion indicates a thyroglossal cyst.
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A 40-year-old woman has a solitary thyroid nodule. Her serum TSH is normal. What is the most appropriate next step in evaluating the nodule?
Correct. A solitary nodule with a normal or raised TSH should proceed to ultrasound and FNAC; a normal TSH does not exclude malignancy. A radionuclide scan is reserved for a suppressed TSH.
Solitary nodule with normal/raised TSH: ultrasound + FNAC. Suppressed TSH: radionuclide scan first.
Do not be reassured by a normal TSH. The pathway is TSH → ultrasound → FNAC. Only a SUPPRESSED TSH justifies a radionuclide scan first to look for a hot (toxic) nodule.
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An FNAC of a thyroid nodule shows cells with overlapping nuclei, nuclear grooves and intranuclear inclusions, and the histology later reveals psammoma bodies. The tumour has spread to cervical lymph nodes. Which thyroid cancer is this, and what is its characteristic mode of spread?
Correct. Psammoma bodies and the nuclear features (grooves, inclusions) with nodal disease are classic of papillary carcinoma, which spreads predominantly via lymphatics.
Papillary: lymphatic spread, psammoma bodies. Follicular: haematogenous, needs histology (capsular/vascular invasion).
Psammoma bodies and nuclear grooves/inclusions = papillary carcinoma, which spreads via lymphatics. Follicular carcinoma spreads haematogenously and cannot be diagnosed by FNAC alone.
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FNAC of a thyroid nodule reports a 'follicular neoplasm'. Why can a definitive diagnosis of follicular carcinoma not be made on FNAC alone?
Correct. Follicular carcinoma is distinguished from a benign follicular adenoma by capsular and/or vascular invasion, which can only be seen on the resected histological specimen, not on cytology.
Follicular carcinoma needs histology (capsular/vascular invasion); FNAC can only say 'follicular neoplasm'.
Cytology cannot show capsular or vascular invasion; the malignant diagnosis of a follicular lesion needs the full histological specimen (usually hemithyroidectomy).
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A patient with a thyroid nodule has a raised serum calcitonin, and family screening reveals a RET proto-oncogene mutation. Which thyroid cancer is this, and from which cells does it arise?
Correct. Medullary thyroid carcinoma arises from parafollicular C cells, secretes calcitonin, and is associated with MEN-2 syndromes and germline RET mutations.
Medullary carcinoma: C cells, calcitonin marker, MEN-2/RET. Screen for phaeochromocytoma before surgery.
Calcitonin and a RET mutation point to medullary carcinoma (parafollicular C cells, MEN-2). The other types arise from follicular epithelium or are undifferentiated.
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An elderly woman presents with a rapidly enlarging, hard, fixed neck mass causing stridor and hoarseness over a few weeks. Which thyroid cancer is most likely and what is its general prognosis?
Correct. A rapidly growing, hard, fixed thyroid mass with airway/voice compromise in an elderly patient is the classic presentation of anaplastic (undifferentiated) carcinoma, which carries a very poor prognosis.
Anaplastic carcinoma: elderly, rapid, fixed, airway compromise, dismal prognosis.
Rapid growth, fixation and airway compromise in the elderly characterise anaplastic carcinoma, the most aggressive type with the worst prognosis. Differentiated cancers (papillary/follicular) generally do well.
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A 55-year-old woman is found to have hypercalcaemia with renal stones, bone pain, abdominal symptoms and low mood. Biochemistry shows raised serum calcium with an inappropriately raised PTH. What is the most likely cause and the definitive treatment?
Correct. Hypercalcaemia with an inappropriately raised PTH is primary hyperparathyroidism, most often from a single adenoma; parathyroidectomy is curative. The symptoms are 'stones, bones, abdominal groans and psychic moans'.
Primary HPT: high Ca + high PTH, usually an adenoma, stones/bones/groans/moans; surgery is curative. Diagnose biochemically before imaging.
Raised calcium with inappropriately raised PTH = primary hyperparathyroidism (usually a single adenoma). Parathyroidectomy is curative; diagnosis is biochemical before any localising scan.
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