During the period, 1990–1999, the histological diagnoses of 317 consecutive thyroid cancers removed by surgery were reviewed. A total of 5,611 surgical specimens resected for benign or malignant disease of the thyroid gland concerning 1,114 males and 4,497 females (M/F-ratio: 1:4) were examined. Seven malignancies in the thyroid gland were excluded (3 sarcomas, 2 Non-Hodgkin-lymphomas, 1 malignant plasmocytoma and 1 metastasis of a clear cell renal carcinoma). 111 of the 310 patients with TC were treated by lobectomy of the right thyroid lobe and 83 of the left lobe, 106 patients had total thyroidectomy. For 10 patients there was no precise clinical site description. The 310 thyroid carcinomas included 248 (80.0%) papillary, 45 (14.5%) follicular, 11 (3.5%) medullary and 6 (2.0%) anaplastic/undifferentiated carcinomas. The 310 carcinomas of the thyroid gland involved 74 males (23.9%) and 236 females (76.1%); M/F-ratio of 1:3.2. The mean age was 48.3 years (range: 13–92). 71 TCs (22.9%) had a multifocal growth pattern. 140 TCs were localized in the right thyroid lobe, 106 TCs in the left lobe and 54 TCs on both sides.
In the follow-up 11.6% of the 310 patients with primary TC developed a second primary malignant neoplasm in other organs. 33 out of the 236 female patients with TC had a subsequent second primary malignant neoplasm, 16 (7.1%) of these were breast cancers, whereas only 3 males out of 74 patients with TC suffered from a second primary carcinoma (larynx, kidney, urinary bladder).
The average, annual, age-specific rate of thyroid carcinomas in Luxembourg over the period 1990–1999 for all ages and both genders was 7.4 per 100,000: for males 3.6 per 100,000 and for females 11.3 per 100,000. The comparison of the crude incidence rates of the patients with TC diagnosed in the two 5-year periods 1990–1994 and 1995–1999 revealed an increase of 36.5% for both genders combined from 6.3 to 8.6 per 100,000, for females by 32.0% from 9.7 to 12.8 per 100,000 and for males by 51.7% from 2.9 to 4.4 per 100,000. Comparing the three 3-year time periods from 1990 to 1998 the overall crude incidence rates of TC in the two first periods, 1990–1992 and 1993–1995, remained stable at 6.3 per 100,000 and 6.0 per 100,000 respectively. In the third period, 1996–1998, there was a significant increase of the crude incidence rate of TC by 53.3%, from 6.0 per 100,000 to 9.2 per 100,000 (p < 0.05). Additional file 1
displays the crude incidence rates of TCs (n = 310 cases) for both genders in relation to the histological subtypes and the tumour sizes over the study period.
The average, annual, age-standardized incidence rate (ASR-world population) of thyroid carcinomas during the study period 1990–1999 was 5.9 per 100,000 for both genders: for males 3.0 per 100,000 and for females 8.8 per 100,000 (Figure ). In Additional file 2
the world age-standardized incidence rates (ASR/W) of TCs in the Luxembourgish population (females and males) over the period 1983–1997 in comparison to other Western European countries, the USA and Canada are presented [7
Time trend of the age-standardized (world population) incidence rates of thyroid carcinomas (n = 310) by gender; 1990–1999.
The total number of TCs rose from 31 cases in 1990 to 45 in 1999 (in females from 24 to 31, in males from 7 to 14). Comparing the two 5-year periods 1990–1994 to 1995–1999, there was a significant increase in the absolute number of all TCs from 126 to 184 cases (p < 0.001). The absolute number of TCs increased significantly in females over the two periods from 98 to 138 cases (p < 0.01), in males from 28 to 46 cases (p < 0.001). In 1997, there was an abnormal two-fold increase of the number of morphologically confirmed TCs especially in middle-aged females, which required further investigations focusing on tumour sizes and the number of surgical treatments.
In our series 124 microcarcinomas – i.e. occult, small TCs with less than 1 cm in diameter – could be identified. 92 of these were of papillary type, 23 of papillary type variant follicular, 6 of follicular type and 3 of medullary type (Figure ). Time trends of variations in tumour sizes (millimetres) are shown in Additional file 1
. Indeed, in 1997 out of 49 TCs, 26 cases (53.1%) were microcarcinomas. This means a statistically significant 2.4-fold increase, in comparison to the average number of microcarcinomas diagnosed over the study period.
Number of TCs stratified by histological type and tumour size; n = 310 cases; period 1990–1999.
During the same time (1990–1999) the number of surgical specimens examined (n = 5,611 cases) remained stable, 532 specimens in 1990 and 531 in 1999. In Figure the annual crude incidence rates of TC and the annual crude incidence rates of the surgical specimens are represented.
Crude incidence rates of invasive thyroid carcinomas and the surgical specimens for benign or malignant diseases for both genders, period: 1990–1999.
The age-distribution of the 310 patients with TC is documented in Figure . In our series only 3 patients (1%) were children or adolescents, whereas 126 patients (40.6%; 98 females/28 males) were between 20 and 44 years old, 155 patients (50.0%; 115 females/40 males) between 45 and 69 years and 26 patients (8.4%; 22 females/4 males) 70 years of age and above.
Age-distribution of the thyroid carcinomas (n = 310 cases); 1990–1999.
The overall observed survival rates of the 310 patients with TC, diagnosed on surgical resection specimens between 1990 and 1999, were calculated and stratified by years: 1-year: 95.2+/-2% (n = 295/310); 2-year: 95.2+/-2% (n = 295/310); 3-year: 93.9+/-3% (n = 291/310); 4-year: 93.2+/-3% (n = 289/310) and 5-year:92.9+/-3% (n = 288/310). The overall observed 3-year survival rate of the 310 patients with TC was 93.9+/-3% (291/310) and the 5-year observed survival rate 92.9+/-3% (288/310).
Over the first study period, 1990–1994, the relative 3-year survival rate of the 126 patients with TC was 93.9+/-4% for both genders (females: 95.5+/-4%; males: 88.2%), the relative 5-year survival rate 94.2+/-4% for both genders (females 95.4+/-4%; males: 90.1%).
In Table the observed 3-, 5- and 10- year survival rates of TC for both genders in relation to the four histopathological types – papillary, follicular, medullary and anaplastic/undifferentiated carcinomas – and the four cohorts <20 years, 20–44 years, 45–69 years and >69 years of age are documented. All patients with differentiated TC aged 44 years or less had good prognosis and all patients survived 5 years. Additional file 3
shows the observed 3-, 5- and 10-year survival rates of TC by time periods, gender and histological type.
Table 1 Overall observed 3-, 5- and 10-year survival rates of TCs for both genders in relation to the 4 age cohorts (<20 years, 20–44 years, 45–69 years and >69 years of age) and the 4 histological types (papillary, follicular, (more ...)
In Table , the observed 5-year survival rate of 253 patients with TC is stratified by tumour size (pT/UICC) and by surgical resection for cure (R0). 14 patients with R1- and R2-status after the first thyroid gland lobectomy got at least one week later total thyroidectomy for cure. 52 patients with TC were classified as Rx-cases because the thyroid gland was removed in several irregular fragments.
Prognoses of differentiated thyroid carcinomas resected for cure (R0)- overall observed 5-year survival rates 1990–1999 stratified by tumour size (253 cases; exclude 6 anaplastic carcinomas).
All 6 patients with an anaplastic/undifferentiated TC died within the first 3 months after the histopathologic diagnosis (survival range: 5–86 days).