RESULTS
During the study period, participation was offered to a total of 506 patients, of whom 429 were valid for evaluation. Figure 1 depicts the flow diagram of the study and the classification of the evaluated patients according to their risk factors. The final population consisted of 301 (70.2%) women and 128 (29.8%) men with a mean age of 49.1±11.0 years and a BMI of 42.6±5.8 kg/m2. Morbid obesity (BMI≥40 kg/m2) was present in 283 (66.2%) patients. As shown, 129 (30.1%; CI 25.9-34.6) patients were classified as having one or more risk factors for thyroid cancer. Abnormal palpation was present in 38 (8.9%; CI 6.5-11.9) individuals. Elevated TSH/hypothyroidism was the most prevalent risk factor (19.6%; CI 16.1-23.6). Prevalence of risk factors was significantly higher among women (34.4% vs 17.4%; P<0.001). Radiation exposure was not present in any patient.
Sixty-nine (16.1%; CI 12.8-19.9) patients harboured thyroid nodules with indication for FNAB according to the ATA guideline [16]. This value was significantly higher than expected (10%; P<0.0001) [15]. Prevalence of thyroid nodules was significantly higher in women (18.9% vs 9.4%; P=0.014). Patients with thyroid nodules were significantly older (54.210.0 vs. 48.212.1; P<0.005). Body mass index was not different between patients with or without thyroid nodules (P=0.49).
Sixty-three patients underwent FNAB. Table 1 shows the FNAB results, the corresponding US risk categories and the final surgical diagnosis when available. Initially, six nodules received a Bethesda 3 diagnosis, which was confirmed in a second FNAB in 2 cases; the second FNAB of the four remaining nodules rendered a Bethesda 2 diagnosis.
Six patients were lost for follow-up before performing the FNAB; two of these nodules were classified as high suspicion pattern according to the ATA guideline (moderately suspicious according to ACR) with a maximum diameter of 12 mm.
Four patients were operated on the basis of cytological results with 3 final cases of papillary thyroid cancer and one case of nodular hyperplasia (cytological diagnosis: Bethesda 4). The clinical and pathological characteristics of papillary thyroid cases are shown in Table 2. An additional case was operated despite a benign FNAB result on the basis of mild local symptoms with a final result of nodular hyperplasia.
In 111 (25.9%) patients, thyroid nodules with no indication of FNAB were found. In 48 (43.2%) patients follow-up sonographies were performed after a median time of 14 months. During follow-up, 26 months after the initial screening, we detected enlarged suspicious lymphadenopathies in a 47yr old male patient with a hypoechoic isthmic nodule of 8mm. The final diagnosis was papillary thyroid carcinoma (multicentric, infiltrative follicular variant) pT1bN1bM0 with a largest nodule of 11mm. At first evaluation, TSH was normal and TPOAbs were undetectable. Therefore, risks of malignancy were 0.93% (CI 0.02-1.84) for the entire screened cohort; 2.2% (CI 0.9-5.5) for patients with thyroid nodules and 5.8% (CI 2.3-14.0) for those nodules with indication of FNAB.
Table 3 depicts the percentage of thyroid nodules according to thyroid palpation and risk factors. As shown, the presence of an abnormal palpation was associated with a significantly higher prevalence of thyroid nodules, whereas the prevalence of thyroid nodules was not dependent on the presence of risk factors. Additional comparisons considering as risk factor a TPOAb level above 100 IU/ml and excluding patients with treated hypothyroidism did not find significant differences between groups in the prevalence of thyroid nodules.
Table 4 shows the prevalence of thyroid nodules according to the individual risk factors. The presence of thyroid nodules was, again, not dependent on the presence of any of the assessed risk factors.