thyroid cancer accounts for approximately 2% of all cancers diagnosed worldwide and 95% of all endocrine cancers . recent reports describe a continuous increase in thyroid cancer incidence worldwide . in certain geographical areas
, this increase exceeds 100% ( and is as high as 250% in some cases ) .
it has been suggested that this generally steady trend of increasing thyroid cancer incidence may be only apparent , and that it depends on higher detection rates of small tumors due to the technological advances in morphological and functional imaging techniques over the last few decades .
thyroid goiter is a pathological condition with epidemic dimensions in some areas because of several geographical , nutritional , and genetic factors .
it has been linked to a higher risk of thyroid cancer , especially the follicular histotype .
the aim of this population - based study was to analyze and describe the epidemiological characteristics and trends of thyroid cancer in the province of sassari ( sardinia , italy ) , an area with epidemic thyroid goiter , in the period 19922010 .
the epidemiological data presented in this paper were obtained from the  registry of the tumors of the province of sassari . 
this registry was created in 1992 by the local health agency for the epidemiological surveillance of tumors in the province . in 1999
, it became part of a wider web of tumor registries , coordinated today by the italian association for tumor registries ( associazione italiana registri tumori ( airtum ) ) .
the association coordinates 34 registries in the country , collects and publishes data , and collaborates with international organizations in the field .
every registry collects data on tumoral diseases affecting inhabitants in the territory of jurisdiction through the local hospitals and health care services , as with other registries ( e.g. , death registries ) .
demographic , clinical , pathological , and prognostic data are collected for each case of cancer and are registered in a digital database .
crude incidence and mortality rates per 100,000 inhabitants per year were calculated , as were standardized rates adjusted for european population standards .
a comparison between incidence and mortality in the province of sassari and those in other italian provinces was performed .
additionally , the cumulative risk of developing the disease and of dying between zero and 74 years of age was estimated .
the age class distribution and time trends of incidence , mortality , mean age of disease onset , and histology were also evaluated .
diagnosis was confirmed by histological or cytological reports in 1,089 cases ( 98.3% ) and using other information sources ( clinical reports , death certifications , etc . ) in the remaining 19 cases ( 1.7% ) . among the 1,108 individuals registered , 237 were males and 871 females , with a male - to - female ratio of 1  :  3.7 .
the cumulative risk of developing the disease was 0.42% for males and 1.49% for females .
the crude incidence of thyroid malignancies in the period under investigation was 5.8/100,000 for men and 20.5/100,000 for women .
table 1 shows the distribution of incidence in relation to age in percentages while table 2 shows the distribution of incidence rates in relation to age .
incidence rates were also calculated for the following three time periods : 19922000 , 20012005 , and 20062010 ( figure 1 ) .
there was a progressive increase in the incidence rate in males , from 3.37/100,000 in the first period to 5.87/100,000 in the second period and 8.13/100,000 in the last period .
the corresponding figures for females were 11.85/100,000 , 22.14/100,000 , and 26.93/100,000 , respectively . a twofold increase in incidence occurred between 1992 and 2010 .
analysis of the trend of mean age at disease onset for the same periods of time did not reveal any relevant changes ( figure 2 ) .
concerning histology , 866 lesions ( 79.5% ) were papillary tumors , 123 ( 11.3% ) follicular , 20 ( 1.8% ) medullary , and 28 ( 2.6% ) other histological subtypes . in the remaining cases ( 4.8% ) ,
an increasing trend with regard to the principal histotypes ( papillary and follicular ) was observed from 1992 to 2010 , while medullary and other rare histotypes remained stable ( figure 3 ) . 

table 3 shows the comparison of the incidence and mortality in the province of sassari with those in other italian provinces .
there were 71 deaths in the period under investigation ( 32 males and 39 females ) .
the cumulative risk of death was extremely low ( 0.05% for males and 0.04% for females ) .
table 2 shows the age - class distribution of mortality rates . there was a steady increase in mortality in relation to age after the fifth decade of life .
figure 1 shows the time trend of mortality between 1992 and 2010 ; there were no significant changes .
thyroid cancer accounts for approximately the 2% of all cancers diagnosed worldwide and 95% of all endocrine cancers .
recent data suggest there were more than 213,000 new cases of thyroid cancer worldwide in 2008 , with a crude incidence rate of 3.1/100,000 and a cumulative risk of developing the disease of 0.31 . the male - to - female ratio was approximately 1  :  3.3 , while the crude incidence for men was 1.4/100,000 and that for women was 4.9/100,000 .
the cumulative risk was 0.15 for males and 0.47 for females . concerning the italian population , we obtained information using the same data source , and the following picture for 2008 was created : 7,448 new cases ( 1,618 males and 5,830 females ) , a crude incidence of 12.5/100.000 ( 5.6 for males and 19 for females ) , and a cumulative risk of 0.88 ( 0.4 for males and 1.35 for females ) .
italy ranks third in europe in terms of new cases , after the russian federation and france .
the standardized incidence of thyroid cancer in the province of sassari was similar to that estimated for the entire country ( table 3 ) .
this is somewhat surprising as sardinia is an area of epidemic thyroid goiter , which is associated with increased incidence of cancer , particularly the follicular type .
this seems not to be the case in our province , where the percentage of follicular thyroid cancers was similar to that in large national and international reports , with only a slight tendency to increase from 1992 to 2010 .
our findings are confirmed by surgical reports published by surgeons employed in local hospitals . in these reports ,
less than 30% of the patients who underwent thyroidectomy for thyroid disease were affected by cancer and the percentage of the follicular subtype , as determined by pathological examination of surgical specimens , was comparable to that found in the present study .
comparisons of the incidence rates with those of other italian provinces place our province approximately in the middle , between provinces with higher incidences , such as ferrara , modena , and reggio emilia , and provinces with lower incidences , such as ragusa and trento . considering the distribution of the disease in relation to age , only approximately 10% of the cases occurred in individuals younger than 30 years and older than 75 .
it is interesting to observe that the peak incidence in men occurred at age 8084 years , while in women it occurred earlier ( at 5054 years of age ) .
while women generally develop the disease earlier in their lives , when they are professionally active and have a long life expectancy , men develop the disease later , probably after their retirement from work and when their life expectancy and probability of dying from the disease are lower .
the time trends analysis showed a stable increase in incidence in the province of sassari .
this trend is common in numerous national and international geographical areas , which have contributed to the global increase in the number of new thyroid cancer cases reported in several publications . as we mentioned before , in certain geographical areas such increases are greater than 100% and as high as 250% in some cases .
it is not clear whether this is a real increase in incidence , as was demonstrated in some areas after nuclear incidents , or whether it reflects a general improvement in the technological means and expertise employed to detect small thyroid malignancies , which in the past may have remained undiscovered [ 3 , 7 ] .
several autopsy studies demonstrated a prevalence of thyroid microcarcinomas ranging from 2% to 35% [ 8 , 9 ] . concerning mortality , only 71 deaths occurred in the 18 years we studied .
crude overall mortality was 0.8/100,000 for men and slightly superior for women ( 0.9/100,000 ) .
these values are similar to those observed in other provinces in italy and in recent european reports [ 5 , 10 ] , but somewhat higher than some worldwide estimates . considering the age - class mortality trend , a natural increase in relation to age was observed in both sexes , with peaks after the eighth decade of life and without significant variations between 1992 and 2010 .
the relative 5-year survival was lower in males than in females , but by global standards it can be considered excellent , especially in relation to other types of malignancies , and suggests that a good local health care system is available for the sufferers .
our data show an increasing trend in the incidence of thyroid cancer in the province of sassari . this trend seems to follow the general worldwide trend and does not seem to be related to the high incidence of thyroid goiter in the area .
the frequencies of the different histological subtypes were similar to those reported in numerous national and international reports .
women are affected earlier than men and therefore suffer greater professional , economic , and social impacts .
overall mortality is low and a relative 5-year survival is excellent , especially in comparison to other malignancies .
 the aim of this study was to analyze and describe the epidemiological characteristics and trends of thyroid cancer in the province of sassari ( sardinia , italy ) , an area with epidemic thyroid goiter , in the period 19922010 . 
 data were obtained from the local tumor registry which makes part of a wider registry web , coordinated today by the italian association for tumor registries . an increasing trend in the incidence of thyroid cancer in the province of sassari was evidenced . 
 this trend seems to follow the general worldwide trend and does not seem to be related to the high incidence of thyroid goiter in the area . 
 the frequencies of the different histological subtypes were similar to those reported in numerous national and international reports . 
 women are affected earlier than men and , therefore , suffer greater professional , economic , and social impacts . 
 overall mortality is low and a relative 5-year survival is excellent , especially in comparison to other malignancies . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusions