Thyroid Adenoma

1. See Also
   1. Multinodular Goiter
2. Epidemiology
   1. Incidence of Thyroid Nodules US: 9 Million per year
      1. Thyroid Carcinoma occurs in 5-10% of palpable Nodules
   2. Prevalence
      1. Women: 7-8% lifetime Prevalence
      2. Men: 2% lifetime Prevalence
      3. Present on autopsy in 50% of cases
3. Signs
   1. Discrete palpable Thyroid Nodules
      1. Small, less than 4 cm
      2. Usually solitary
   2. Usually cold Nodule on Thyroid scan
      1. Only 1% are active Nodules (Hyperthyroidism)
4. Evaluation
   1. Step 1: Identify palpable Nodule on exam
   2. Step 2: Obtain TSH
      1. Hyperthyroidism: Go to Step 3
      2. Euthyroid: Go to Step 4
   3. Step 3: Obtain Radioactive Thyroid Scan
      1. Hot Nodule
         1. Euthyroid: No further testing
         2. Hyperthyroidism: Consider Radioactive Iodine
      2. Cold Nodule
         1. More likely to be malignant (5-15% of cases)
         2. Go to Step 4
   4. Step 4: ThyroidUltrasound
      1. Benign appearing Nodule <1 cm with negative clinical history
         1. Observe and follow
      2. Nodule >1 cm
         1. Cystic lesion
            1. Simple drainage
         2. Solid Lesion
            1. Go to Step 5 (FNA)
   5. Step 5: Fine needle aspiration (FNA)
      1. Consider Ultrasound guided FNA
      2. Benign
         1. Consider repeating FNA in 6 months
         2. Consider repeat ThyroidUltrasound every 1-2 years
      3. Suspicious: Frozen section
         1. Consider Thyroid lobectomy if still inconclusive
      4. Malignant: Thyroidectomy
5. Differential Diagnosis
   1. Thyroid Carcinoma (5-10% in adults, 14-40% in children)
   2. Dominant follicle in Multinodular Goiter (23%)
   3. Thyroid cyst (simple or mixed)
   4. Thyroiditis
   5. Thyroid Adenoma
      1. Simple or colloid Macrofollicular Adenoma
         1. Most common type
         2. Follicles of normal size
      2. Embryonal (Trabecular) adenoma
         1. Mostly stroma and minimal follicles
      3. Fetal Microfollicular Adenoma
         1. Small follicles with minimal colloid
         2. Follicular cancer found in 5% of cases
      4. Hurthle Cell Adenoma (uncommon)
6. Monitoring
   1. Slow serial growth of benign Thyroid Nodules
      1. Unlikely to be malignant if initial FNA negative
      2. Alexander (2003) Ann Intern Med 138:315-8
7. References
   1. Boigon (1995) Postgrad Med 98(2):73-80
   2. Giuffrida (1995) Am J Med 99(6):642-50
   3. Mazzaferri (1993) N Engl J Med 328:553-9
   4. Walsh (1999) Clin Otolaryngol 24:388-97
   5. Welker (2003) Am Fam Physician 67(3):559-74