A 36-year-old woman comes to the physician for a follow-up visit after she had a PET scan that showed a nodule on the thyroid gland. She has no difficulty or pain while swallowing. She was treated for non-Hodgkin lymphoma at the age of 28 years, which included external beam radiation to the head and neck and 4 cycles of chemotherapy. She appears healthy. Vital signs are within normal limits. Physical examination shows no abnormalities. Serum studies show: Glucose 82 mg/dL Creatinine 0.7 mg/dL Thyroid-stimulating hormone 3 μU/mL Ultrasound of the neck shows a 1.2-cm (0.5-in) nodule on the left lobe of the thyroid with irregular margins and microcalcifications. A fine-needle aspiration biopsy shows Psammoma bodies and cells with clear, ground-glass, empty nuclei. Which of the following is the most appropriate next step in management?

Observation and follow-up in 3 months

A 74-year-old retired female teacher is referred to the endocrinology clinic. She is very concerned about a large mass in her neck that has progressively enlarged over the past 2 weeks. She also reports a 15 pound weight loss over the last 3 months. She now has hoarseness and difficulty swallowing her food, giving her a sensation that food gets stuck in her windpipe when she swallows. There is no pain associated with swallowing. Her speech is monotonous. No other gait or language articulation problems are noted. Testing for cranial nerve lesions is unremarkable. On palpation, a large, fixed and non-tender mass in the thyroid is noted. Cervical lymph nodes are palpable bilaterally. The patient is urgently scheduled for an ultrasound-guided fine needle aspiration to guide management. Which of the following is the most likely gene mutation to be found in this mass?

Inactivating mutation of the p53 tumor suppressor gene

Activating mutation of the Ras protooncogene

A 30-year-old woman is brought to the urgent care clinic by her husband. She complains of numbness around her lips and a tingling sensation in her hands and feet. She underwent near-total thyroidectomy for an enlarged thyroid gland a month ago. Vital signs include: blood pressure is 130/70 mm Hg, pulse is 72/min, respiratory rate is 16/min, and temperature is 37.0°C (98.6°F). A surgical incision scar is present in the anterior aspect of the neck. The attending physician inflates the blood pressure cuff above 150 mm Hg and observes the patient a couple of minutes while measuring her blood pressure. The patient develops sudden stiffness and tingling in her hand. Blood test results are as follows: Hemoglobin (Hb%) 10.2 g/dL White blood cell count 7000/mm3 Platelet count 160,000/mm3 Calcium, serum (Ca2+) 6.0 mg/dL Albumin 4 g/dL Alanine aminotransferase (ALT), serum 15 U/L Aspartate aminotransferase (AST), serum 8 U/L Serum creatinine 0.5 mg/dL Urea 27 mg/dL Sodium 137 mEq/L Potassium 4.5 mEq/L Magnesium 2.5 mEq/L Urinalysis shows no white or red blood cells and leukocyte esterase is negative. Which of the following is the next best step in the management of this patient?

Serum parathyroid hormone (PTH) level

CT scan abdomen with pancreatic protocol

A 55-year-old woman comes to the physician because of a 4-month history of a painless lump on her neck. Examination shows a hard nodule on the left side of her neck. A fine-needle aspiration biopsy shows well-differentiated cuboidal cells arranged spherically around colloid. She undergoes thyroidectomy. Histopathological examination of the surgical specimen shows invasion of the thyroid capsule and blood vessels. Which of the following cellular events is most likely involved in the pathogenesis of this patient's condition?

PAX8-PPAR gamma gene rearrangement

Activation mutation in the BRAF gene

Mutation in the RET proto-oncogene

p53 tumor suppressor gene inactivation

Thyroid cancer management — USMLE Lesson

🔬 Pathology - The Cancer Quartet

Type	Prevalence	Histology Buzzwords	Key Features
Papillary	~85%	Orphan Annie eyes, psammoma bodies, nuclear grooves	Excellent prognosis; lymphatic spread
Follicular	~10%	Capsular/vascular invasion	Hematogenous spread (bone, lung)
Medullary	~3%	Amyloid stroma (Congo red+), polygonal cells	From parafollicular C-cells; ↑ Calcitonin
Anaplastic	<2%	Pleomorphic giant cells	Elderly; dismal prognosis; local invasion

⭐ Medullary Thyroid Cancer (MTC) is associated with MEN 2A and 2B syndromes. Always test for RET proto-oncogene mutations.

🕵️ Diagnosis - Nodule Detective Work

The primary goal is to identify the ~5-10% of nodules that are malignant.

Step 1: TSH Level
- If TSH is low (↓), suspect a hyperfunctioning ("hot") nodule.
Step 2: Imaging
- Low TSH: Radionuclide Iodine Uptake (RAIU) scan.
  - "Hot" nodule: Benign. Treat hyperthyroidism.
  - "Cold" nodule: Higher malignancy risk. Proceed to FNA.
- Normal/High TSH: Thyroid Ultrasound (US) is the next step.
Step 3: Fine-Needle Aspiration (FNA)
- Gold standard, guided by US.
- ⚠️ Suspicious US features: Microcalcifications, hypoechogenicity, irregular margins, taller-than-wide.

Ultrasound features of suspicious thyroid nodules

⭐ FNA is highly accurate but has a key limitation: it cannot distinguish follicular adenoma from follicular carcinoma. This distinction requires surgical excision to assess for capsular or vascular invasion.

🔪 Management - The Surgeon's Scalpel

Surgical approach is tailored to tumor type, size, and risk factors.

Post-Op Adjuncts & Monitoring:
- Radioactive Iodine (RAI; ¹³¹I): For remnant ablation post-total thyroidectomy in high-risk differentiated cancers.
- TSH Suppression: Levothyroxine therapy to keep TSH low, reducing growth stimulus.
- Tumor Markers: Monitor Thyroglobulin (Tg) for papillary/follicular; Calcitonin for medullary.

Thyroidectomy: RLN and parathyroid gland identification

⭐ Post-thyroidectomy, always monitor for hypocalcemia (Chvostek/Trousseau signs). It's the most common complication due to inadvertent parathyroid gland removal or devascularization.

⚠️ Complications - Post-Op Pitfalls

Hypocalcemia (↓ $Ca^{2+}$): Most common; due to parathyroid injury/removal.
- S/S: Perioral numbness, paresthesias, Chvostek/Trousseau signs.
- Tx: IV calcium gluconate (severe), oral calcium & calcitriol.
Recurrent Laryngeal Nerve (RLN) Injury:
- Unilateral: Hoarseness, breathy voice.
- Bilateral: Stridor, airway obstruction → emergent airway.
Superior Laryngeal Nerve (SLN) Injury: Loss of high-pitched voice.
Hematoma: Neck swelling, can cause rapid airway compression.

⭐ Bilateral RLN injury is a surgical emergency causing acute airway obstruction from unopposed vocal cord adduction.

Thyroid gland, recurrent and superior laryngeal nerves

⚡ Biggest Takeaways

Papillary is most common; look for Orphan Annie eyes, psammoma bodies, and lymphatic spread.

Follicular spreads hematogenously; diagnosis requires capsular/vascular invasion on final pathology.

Medullary arises from C-cells, produces calcitonin, and is linked to MEN 2 (RET).

Anaplastic is a rapidly fatal cancer in the elderly.

Workup: Ultrasound first, then Fine-Needle Aspiration (FNA) is the best initial diagnostic test.

Treatment: Surgery is primary, followed by radioactive iodine and TSH suppression.

Monitor recurrence with thyroglobulin (papillary/follicular) or calcitonin (medullary).

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