The Prevalence of Occult Medullary Thyroid Carcinoma at Autopsy

CONTEXT: The prevalence of occult medullary thyroid carcinoma (MTC) in the general population is unknown but may be important when considering strategies to diagnose clinically relevant MTC in nodular goiter or other populations. OBJECTIVE: Our objective was to determine the prevalence of occult MTC in a series of autopsies. DESIGN: We conducted a systematic review of autopsy series from 1970 to present using a PubMed search. PATIENTS: The patients came from 21 countries, ages ranged from 6-95 yr, both genders were represented, and none had clinical evidence of thyroid disease before autopsy. INTERVENTION: Three series were excluded based on tumor size less than 500 μm, non-English language, or insufficient information. MAIN OUTCOME MEASURE: Prevalence of occult MTC was calculated. RESULTS: An average prevalence of 0.14 and 7.6% for occult MTC and papillary thyroid carcinoma, respectively, was found among 7897 autopsies from 24 published series. Greater than 75% of patients with MTC were more than 60 yr old, and male to female ratio was comparable. Tumor size was virtually all subcentimeter, and there was no lymph node spread, extrathyroidal extension, or distant metastases reported. CONCLUSIONS: A small number of people in the general population, who do not have known thyroid disease, have occult MTC and die of other causes. This finding of untreated occult MTC without morbidity or mortality should be considered in population prevalence studies, when strategies to detect thyroid neoplasia are considered (e.g. serum calcitonin or ultrasound), and included in cost-effectiveness models of routine serum calcitonin screening for nodular thyroid disease.