02/02/2026
4 Types of THYROID CANCER USMLE Will Test on Step 1, Step 2, & Step 3
1️⃣ Papillary Carcinoma
🔬 Most common (80%). best prognosis
They’ll give you young woman with painless nodule, history of childhood radiation, cervical lymphadenopathy.
⚠️ Spreads via LYMPHATICS but still excellent prognosis.
Histology: “Orphan Annie” eyes (clear nuclei), nuclear grooves, psammoma bodies.
🔍 Dx: Ultrasound → FNA shows characteristic nuclear features.
🏥 Tx: Total thyroidectomy + radioactive iodine (I-131) ablation + TSH suppression. >95% survival.
2️⃣ Follicular Carcinoma
🔬 Second most common. spreads via BLOOD
They’ll give you middle-aged patient with nodule.
FNA says “follicular neoplasm”. cannot distinguish adenoma from carcinoma on FNA.
⚠️ Spreads hematogenously to bone and lungs, NOT lymph nodes.
Need surgical excision to see capsular/vascular invasion.
🔍 Dx: FNA indeterminate → lobectomy required to diagnose.
🏥 Tx: Total thyroidectomy + radioactive iodine + TSH suppression.
🎯 FNA “follicular neoplasm” + need surgery to diagnose + mets to bone/lung = Follicular
3️⃣ Medullary Carcinoma
🔬 Parafollicular C cells. CALCITONIN
They’ll give you thyroid mass + elevated calcitonin + diarrhea.
Ask about MEN2A (pheo, hyperparathyroidism) or MEN2B (marfanoid, mucosal neuromas).
⚠️ 25% familial (RET mutation).
Histology shows amyloid deposits.
Screen for pheo BEFORE surgery in MEN2.
🔍 Dx: Elevated calcitonin. RET genetic testing. FNA with calcitonin stain.
🏥 Tx: Total thyroidectomy + lymph node dissection.
NO radioactive iodine. C cells don’t take it up.
🎯 Calcitonin elevated + amyloid + MEN2 = Medullary
4️⃣ Anaplastic Carcinoma
🔬 Undifferentiated. WORST PROGNOSIS
They’ll give you elderly patient (>60) with rapidly enlarging, rock-hard fixed mass causing dysphagia, hoarseness, stridor.
⚠️ Median survival 6 months.
Does NOT respond to radioactive iodine or TSH suppression.
🔍 Dx: FNA shows undifferentiated cells. CT for invasion.