THYROID TUMORS


Benign thyroid tumors

  1. Divided histologically into follicular (89%), papillary, & Hurthle cell
  2. All present as a single thyroid lump
  3. Can produce thyrotoxicosis ("hot nodule" on T-scan)

Malignant thyroid tumors

I. Epidemiology
  1. Female:Male 3:1
  2. Mean age at diagnosis is early 40's
  3. Diagnosis at age < 20yo or > 45yo is associated with shorter survival
  4. Prognosis tends to be worse in male patients
  5. Risk factors include radiation exposure in childhood to head and neck and family history
  6. Most common histologic types: papillary and follicular (tend to be well-differentiated and functioning)
    1. 80% of thyroid cancers are papillary; 10% are follicular
    2. Follicular associated with higher mean age at diagnosis (median mid-50's) and is more commonly seen in iodine-deficient regions than papillary
  7. Medullary carcinoma (a neuroendocrine tumor; part of multiple endocrine neoplasia 2 syndrome)
  8. Anaplastic thyroid cancer: Highly aggressive; may develop from a papillary cancer
  9. Mean 10-year survival as of 2012:
    1. Papillary: 93%
    2. Follicular: 85%
    3. Medullary: 75%
    4. Anaplastic: < 10%
II. Clinical features
  1. Usually asymptomatic at time of diagnosis (often incidentally noted on physical exam or imaging tests e.g. ultrasound)
  2. Can be associated with cervical lymphadenopathy or hoarseness
III. Diagnosis
  1. Ultrasound is the preferred initial study for evaluation of a thyroid nodule.  Features that suggest a possibliity of malignancy include microcalcifications, irregular margins to a nodule, and others.
  2. Avoid CT with IV contrast because the iodinated contrast material may suppress (for several weeks) uptake of I-131 subsequently given for treatment
  3. Fine-needle aspiration useful for diagnosis but is highly specific only for papillary cancers
IV. Treatment
  1. Primary treatments are surgery and (except for medullary and anaplastic), radioiodine as an adjunctive treatment
    1. For well-differentiated cancers < 1cm in size, subtotal thyroidectomy (as opposed to total) may be an option, which offers lower risk of nerve injury or iatrogenic hypoparathyroidism
    2. For cancers > 1cm in size, total thyroidectomy, often with elective node dissection, is often performed (neck ultrasound is not sufficient to rule out nodal involvement)
  2. Medullary cancers and anaplastic  may be treated with tyrosine kinase inhibitors e.g. sorafenib (Nexavar), sunitib (Sutent), pazopanib (Votrient), and vandetanib (Caprelsa)
  3. Anaplastic cancers may be treated with radiation and other chemotherapy
  4. Long-term management after initial treatment
    1. Levothyroxine supplementation to suppress TSH levels to < 0.1 microunits/L
    2. Periodic monitoring of serum thyroglobulin (a marker for thyroid cancer recurrence after total thyroidectomy or partial thyroidectomy + radioiodine ablation)-If trends upward consider radioiodine or PET scan
(Sources include Core Content Review of Family Medicine, 2012)