Cause:Most cases occur as sporadic events in the population; increased incidence from radiation under age 20 yr, w risk thereafter peaking over 20 yrs then declining, eg, 1.7% at 20 yr after radiation rx of Hodgkin's (Nejm 1991;325:599); no increase after 131I rx of Graves' disease (Nejm 1980;303:188)
Pathophys:Often multifocal from multiclonal origins (Nejm 2005;352:2406). Local invasion and metastases (primarily lymphatic), less often bloodborne metastases
75-90% of all thyroid cancers; mean age at dx is 45 yr. Female/male = 2-3:1
Sx:Neck mass
Si:
Thyroid mass (80%), 40% of the time in an abnormal gland from other thyroid disease
Stage at dx:
Excellent, 90% >30-yr survival for stages I and II; worse if age >50 yr, >4 cm diameter, or local or distant metastases. Patients with positive lymph nodes may have equal survival to those with negative nodes
Radiation-induced cancers have same course as others (Ann IM 1986;105:405)
r/o follicular, and undifferentiated carcinomas, including giant cell, small cell, and medullary carcinoma (see Medullary Carcinoma of Thyroid ("Amyloid Struma"))
Lab:
Chem:No helpful preop tests, postop is useful to follow thyroglobulin levels (>10 ngm/cc) as a tumor marker, esp of mets
Path:Aspiration biopsy (Thyroid Nodule) anything over 8 mm (Jama 2006;295:2164, 2177) and cytology; "rug fringe" effect, ie, papillae, but few mitoses; unlike well-formed follicles of follicular or anaplasia, with giant or small cells of undifferentiated types
Xray:Scan usually cold (Ann IM 1978;88:41). Ultrasound can help distinguish benign from malignant (J Clin Endocr Metab 2002;87;1941)
Rx:
Detect in irradiated patients w q1yr thyroid physical exam w bx of any nodules; debated if thryoid hormone suppression helps
Surgical thyroidectomy; lobectomy alone is inadequate even for stage I and II disease (4% vs 14% 30-yr recurrence); up to 14% get cmplc of surgery including hypoparathyroidism and recurrent laryngeal nerve injury. Postsurgical 131I rx (Ann IM 1998;129:622) w thyroid hormone suppression
Chemotherapy possible if metastases with adriamycin (Nejm 1974;290:193), 5-FU, and cisplatin but none very good