Epidemiology of Thyroid Microcarcinoma Found in Autopsy Series Conducted in Areas of Different Iodine Intake

Abstract

The prevalence of thyroid microcarcinomas found at autopsies is 100-1000 times higher than in clinical cancer. The epidemiological and histological characteristics of thyroid microcarcinomas in consecutive series of autopsies performed in two areas of different iodine intake were investigated. Iodine deficient (ID) area: n = 222 (M = 109, F = 113), median age: 74-76 years, median iodine excretion (MIE) of nursing home residents from this area: 70 microg/g creatinine. Iodine sufficient (IS) area: n = 221 (M = 132, F = 89), median age: 68 years, MIE: 500 microg/g creatinine. When compared to the IS area, the results obtained in the ID area showed a higher thyroid weight (mean 27.75 g +/- 18.43 g vs. 16.5 g +/- 9.6 g, p < 0.0001) and a larger number of goitrous glands (50/222 vs. 5/221, p < 0.0001). Altogether 21 microcarcinomas were found (4.74%) with no iodine intake- or gender-related difference: ID n = 11 (4.95%), M/F = 8/3; IS n = 10 (4.52%), M/F = 6/4. Microcarcinomas seemed to be more prevalent in the 40-59-year age group. All microcarcinomas were of the papillary type. In conclusion, compared to clinical cancer, thyroid microcarcinomas are characterized by a two-scale higher prevalence, are not related to iodine intake, gender or nodularity, are most exclusively of the papillary type.

Thyroid papillary microcarcinoma: a descriptive and meta-analysis study

“…In a single ethnic group, it has been observed that the autopsy prevalence of PTMC was not affected by iodine intake (80).…”

“…This may be related to radiation exposure during the bombing of Hiroshima and Nagasaki, but is probably due to ethnicity since Japanese residing in Hawaii, not exposed to bomb radiation, have a similar prevalence of thyroid microcarcinoma, 24% (37,79). In 4620 autopsy cases, PTMC was observed in 9.9% when only a suspected lesion was examined and in 15.5% of 1262 autopsy cases when the entire gland was examined (13,29,37,59,75,76,(80)(81)(82)(83)(84)(85). Therefore, the prevalence of occult thyroid microcarcinoma increases with the extent of the examination of the thyroid, in particular with the thinness of the anatomical slices of the thyroid specimens (29).…”

An Epidemiological Analysis of Thyroid Cancer in a Spanish Population: Presentation, Incidence and Survival

“…The improvement in diagnostic tools (image procedures and fineneedle aspiration biopsy) (Colonna et al, 2007;Scheiden et al, 2006) and greater extensiveness and number of thyroidectomies performed, which makes it easier to detect MPTCs (Leenhardt et al, 2004a), has been suspected to be of etiological importance in the observed increase of papillary thyroid cancer. One study (Kovacs et al, 2005) estimated the prevalence of thyroid microcarcinomas found at autopsies is 100-1000 times higher than in clinical cancer; they were not related to iodine intake and were exclusively of the papillary type (MPTC). It suggests that a large proportion of the population probably lives with undetected thyroid cancer and fits with the hypothesis of an apparent increase in thyroid cancer incidence.…”

Papillary Thyroid Microcarcinoma - Do Classical Staging Systems Need to Be Changed?

“…The second form is a "silent PTMC," a tumor incidentally discovered that will never be apparent and that may be in concordance with the occult carcinoma detected in thyroid glands from autopsies. In this regard, it is interesting to note that gender distribution of PTMC found in autopsies shows differences as compared to clinical papillary tumors [Kovács et al, 2005]. It is well established that the incidence of PTC in women is significantly higher than that in men (with a female to male ratio greater than 2 to 1) [Yao et al, 2011].…”

“…It is well established that the incidence of PTC in women is significantly higher than that in men (with a female to male ratio greater than 2 to 1) [Yao et al, 2011]. However, several authors have not found any significant gender-related differences in PTMC found at autopsies [Lang et al, 1988;Neuhold et al, 2001;Kovács et al, 2005].…”