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numerous studies have shown a worldwide increase in the incidence of thyroid cancer ( tc ) in recent years   due to the increased frequency of papillary thyroid carcinoma ( ptc ) .
the reason for this increase is not well understood , although some authors argue that excessive medicalization , sometimes called 
thus , a greater number of ultrasound scans ( us ) and other imaging techniques , along with an increase in the number of thyroidectomies for benign conditions and better histological examination of surgical specimens , have led to the diagnosis of ptc cases with low clinical impact .
this argument is corroborated by epidemiological data which suggest that the increase in the diagnosis of ptc is at the expense of smaller tumors , especially microcarcinomas ( ptc < 1 cm ) .
other authors , however , point to a real increase in the incidence of ptc , which could be related to the effect of ionizing radiation or iodine supplementation in the general population .
other reasons , such as hormonal factors , the increased incidence of obesity , environmental toxins such as polybrominated diphenyl ethers , or changing histological criteria for ptc   have also been postulated .
the aim of this study was to retrospectively analyze a series of thyroidectomies performed at our center over the course of a decade ( 2001 - 2010 ) and to determine the incidence of tc in these cases .
between january 2001 and december 2010 , a total of 1,323 subjects underwent thyroid surgery .
all included patients had a solitary nodule or a multinodular goiter detected by clinical examination , us , or both .
a fine - needle aspiration biopsy ( fnab ) was performed for thyroid nodules > 1 cm and for nodules < 1 cm with suspicious us features .
thyroidectomy was prescribed for patients with malignant , suspicious , or repetitive indeterminate nodules according to fnab results . moreover ,
surgery was indicated for benign disease when local symptoms were present or for esthetic reasons .
total cohorts were separated into two groups : group 1 included patients operated on between 2001 and 2005 , whereas group 2 included patients operated on between 2006 and 2010 . in both groups , demographic characteristics ,
type of surgery ( total thyroidectomy vs. non - total thyroidectomy ) , preoperative serum levels of thyrotropin ( tsh ) , presence of thyroid antibodies , and incidence of tc according to histological types were compared .
histological variants were classified as differentiated tc ( dtc ) , including ptc and follicular thyroid carcinoma ( ftc ) , and non - dtc , which included all other types of malignancies ( medullary carcinoma , undifferentiated carcinoma , metastatic thyroid , and lymphoma ) . finally , we compared the characteristics of ptc detected in both periods in relation to the following variables : age , preoperative tsh value , tumor size , percentage of microcarcinomas , mutlifocality , lymph node metastases , associated thyroiditis , and mode of diagnosis ( incidental vs. non - incidental ) .
we defined an incidental diagnosis as ptc diagnosed at final histology in a patient whose reason for intervention was benign thyroid disease .
quantitative variables were expressed as mean and standard deviation , and categorical variables were expressed as frequencies and proportions .
statistical analysis was performed using the  test for categorical variables and the student t test for quantitative variables .
a total of 1,263 cases , 1,023 women and 240 men ( average age of 51.9 years ) , were included retrospectively .
thyroidectomy was prescribed for malignancy or suspicious of malignancy in 221 patients ( 17.5% ) .
final histological examination revealed the presence of tc in 253 cases ( 20% ) , and of these , 216 patients had dtc ( 195 ptc cases , 21 ftc cases ) ( fig .
the mean size of the ptc was 15.4 ( 12.6 ) mm , and no significant differences in size were observed over the 10 years ( fig .
group 1 included 593 cases ( 487 women and 106 men ) with a mean age of 51.8 ( 14.2 ) years . in group 2 , there were 670 subjects ( 536 females and 134 males ) with a mean age of 51.9 ( 16.3 ) years .
however , there was a significant increase in the number of malignancies in the second period : 90 tc cases ( 15.2% of all interventions ) in group 1 compared to 163 cases ( 24.3% ) in group 2 ( p < 0.001 ) .
differences were due to a significant increase in the number of dtc cases : 73 ( 12.1% ) in the first half of the decade versus 143 ( 21.3% ) in the second half ( p < 0.001 ) . within dtc cases , there was no significant variation in the number of ftc cases : 7 ( 1.2% ) in group 1 compared to 14 ( 2% ) in group 2 ( p = 0.29 ) . thus , the observed increase in the incidence of tc was due solely to an increase in ptc : 66 cases between 2001 and 2005 , accounting for 11.13% of all thyroidectomies performed , compared to 129 cases between 2006 and 2010 , which accounted for 19.25% of all surgical interventions .
non - dtc thyroid malignancies included 13 and 11 medullary tcs , 5 and 3 anaplastic tcs , and 1 and 6 other tumors ( secondary metastasis and primary thyroid lymphoma ) in groups 1 and 2 , respectively .
the preoperative tsh value was 1.8 ( 5.9 ) mu / dl in group 1 patients and 1.5 ( 1.9 ) mu / dl in group 2 patients .
although not statistically significant , there was an increase in the number of total thyroidectomies in the second half of the decade : 409 cases ( 69% ) between 2001 and 2005 compared to 494 cases ( 73.7% ) between 2006 and 2010 ( p = 0.06 ) . in both groups ,
it can be seen that there were no differences in any of the observed variables , which included age , preoperative tsh value , tumor size , percentage of microcarcinomas , multifocality , metastatic disease , thyroiditis , and mode of diagnosis .
thus , there were a total of 84 incidental cancers , 31 in the first period ( 47% ) and 53 in the second period ( 41% ) ( p = 0.43 ) .
these numbers represented 7.6% of the patient cohort with total thyroidectomies in group 1 and 10.7% of the patient cohort with total thyroidectomies in group 2 ( p = 0.1 ) .
in addition , only 6 cases ( 9% ) in the first period and 12 cases ( 9% ) in the second period were non - incidental microcarcinomas .
this study supports , in our environment , the trend of increased incidence of tc , due to an increase in ptc , during the first decade of the century in the cohort of patients who underwent thyroid surgery .
the percentage of ptc increased by almost 10% between 2006 and 2010 compared to 2001 and 2005 .
one presumed reason for this increase in the incidence of ptc is the screening effect , namely the higher and better performance of various tests in the general population , such as us and fnabs of thyroid nodules , which has led to increased diagnosis of ptc .
this argument is corroborated by epidemiological data suggesting an increase in ptc diagnosis at the expense of smaller ptcs , especially microcarcinomas .
it has been hypothesized that if the entire pool of occult ptc were identified antemorten , the resulting ascertainment bias could result in a 50-fold increase in the apparent incidence of ptc . in our study , we did not observe an increase in microcarcinomas , and the average size of ptc did not change over the decade .
furthermore , although it is postulated as being more frequent , not all reports found that the increase in ptc was only at the expense of smaller ptcs .
davies and welch   found , based on data from the national cancer institute 's surveillance , epidemiology and end results ( seer ) program , that between 1988 and 2002 , the largest percent increases in ptc were in tumors < 2 cm .
hughes et al .   also analyzed the seer registry and found that the greatest increase in ptc occurred in patients older than 45 years with microcarcinomas ; the authors attributed these findings to overdiagnosis . however , using the same database , zhu et al .  
found that the rate of the age - adjusted incidence showed a significant increase in ptc for all tumor sizes between 1988 and 2003 . in a detailed analysis conducted by enewold
, the authors found that ptcs > 5 cm increased 222% ( similar to the 248% in tumors < 1 cm ) in american white women .
similarly , yu et al .   compared the incidence of ptc in two different periods ( 1992 - 1996 and 2000 - 2004 ) and found a significant increase in all tumor sizes .
also , in an italian study that compared the most recent periods ( 1998 - 2003 and 2004 - 2009 ) , the authors did not find differences in the percentage of microcarcinomas .
finally , morris and myssiorek   reported a similar increase in the percentage of cases with extrathyroidal extension , a factor that does not support the screening effect as the cause of the observed changes .
similar to other studies on the incidence of neoplasms , data are recorded in relation to the reference population ( usually per 100,000 population ) . since a high percentage of ptc cases are incidentally diagnosed after thyroidectomies for benign disease , the population incidence of thyroid interventions and the extent of the thyroidectomy may influence this kind of malignancy . in a recent report , sassolas et al .  
found that 64% of microcarcinomas are diagnosed incidentally ; in a study by alevizaki et al .
the frequency of tc was not related to the general population , but to cases of thyroidectomies performed .
we observed an increment in the percentage of interventions that were positive for malignancy , reaching 24.3% in the second period . using a similar design , sassolas et al .   found that 22% of all thyroid interventions for any cause were related to tc .
it has been proposed that the increase in ptc may be due to an improvement in the selection of patients referred for surgery . however
, the fact that incidental and non - incidental cases increased in parallel does not support this hypothesis . in the present study ,
the combination of lack of specific increasing trends of smaller tumors and stability in the percentage of cases incidentally diagnosed seems to favor a true increase in the incidence of ptc .
moreover , in most recent years , there have been no substantial changes in the diagnosis and therapeutic management of patients with nodular thyroid disease .
thus , it appears that the increase in ptc is due to both improvements in diagnostic techniques and their high use ( overdiagnosis ) , and a real increase in the incidence of ptc .
the study population is not representative of the general population nor is it a population with thyroid disease .
therefore , we can not rule out bias caused by changes in social or demographic parameters in the reference population .
moreover , the comparison periods were two successive 5-year periods , a very short time interval for the identification of significant changes in incidence trends .
however , the relatively short study period also reduced the likelihood of changes in socio - demographic status , referral criteria , surgical indications , and diagnostic ( clinical and histological ) and therapeutic protocols .
therefore , this variability could be higher in studies that compare longer periods and thus produce greater bias . in conclusion , this study suggested an increase in the number of tc cases in the first decade of the century in patients undergoing thyroid surgery .
backgroundnumerous studies have shown an increase in the incidence of thyroid cancer ( tc ) in recent years.objectivesin this paper , we reviewed the incidence of tc in a series of patients undergoing thyroid surgery at a single institution over a 10-year period.patients and methodsthe cohorts were divided into two periods ( 2001 - 2005 and 2006 - 2010 ) with the purpose of comparing various clinicopathologic variables.resultsa total of 1,263 patients were included . 
 a significant increase in the number of malignancies was shown in the second period , namely 90 cases in 2001 - 2005 ( 15.2% of all interventions ) compared to 163 cases in 2006 - 2010 ( 24.3% ) ( p < 0.001 ) . 
 these differences were attributed to an increase in papillary thyroid carcinoma ( ptc ) , as there were 66 ptc cases in the first period ( 11.13% of thyroidectomies performed ) compared to 129 cases in the second period ( 19.25% ) . 
 there were no clinicohistological differences among ptc cases in these two periods.conclusionsover the last decade , there has been an increase in the incidence of tc in patients undergoing thyroid surgery . 
 this increase is exclusively due to increases in ptc . 
 our study verifies the existence of this trend in our geographical area , similar to that noted in other parts of the world .