Differentiated thyroid cancer (DTC) is an important clinical entity in our population (Novara, Piedmont, Italy) which is characterized by important environmental influences, as iodine deficiency (ID) and subsequent supplementation, thyroiditis and occupational exposure. To evaluate the features of DTC in our population 20 years after the iodine-prophylaxis pondering the effects of the introduction of the new guidelines for diagnosis and management of DTC after 2005. 322 patients [244 females, age: mean (±SD) 53.8 ± 15.8 years] treated for DTC in a tertiary care center between 1997 and 2010 were retrospectively evaluated. Medical history, demographics, and pathological features were considered. Patients were subdivided into two groups: A (n = 139, diagnosis 1997–2005) and B (n = 183, diagnosis 2006–2010). The population of group A showed a mild ID, while normal iodine status was recorded in group B. A significant increase in histological tumor-associated thyroiditis was found from group A to B (p = 0.021). Recurrent or persistent diseases were found to be correlated with lymph nodes metastases and/or a distant disease at diagnosis, stimulated thyroglobulin levels at the first follow-up and an additional radioiodine therapy. Twenty percent of our patients were females employed in textile industries. The tumor-related inflammation and the occupational exposure should be considered as important factors in the pathogenesis of DTC. Further studies are required in order to confirm our findings.