Thyroid nodules coexisting with either cystic or solid breast nodules: a new clue for this association between nodules coming from ultrasonography

Background: Thyroid and breast nodules (BNs) are common, their prevalence varying based mainly on the population (including age, residence in area of different iodine availability) studied and methods used. The coincidence of thyroid and breast diseases remains controversial and the majority of the studies evaluate the association between breast cancer and thyroid disorders. Here we describe our experience of such association in a non-oncological series. Methods: Between the years 2000 and 2005, 3,372 patients from outpatient clinics were referred for thyroid ultrasonography (US) at our University Hospital; concurrent breast US in the 1,896 women revealed the presence of BNs in 127. The 127 women were divided into two groups, based on the cystic or solid nature of the BN(s). Results: In 84/127 (66.1%) the single or multiple BN was/were cystic (group 1), while in the remaining 43 (33.9%) the single or multiple BN was/were solid [group 2; 19/43 had one thyroid nodule (TN) and the remaining 24/43 had ≥2 TNs]. When BN were cystic the coexisting TN(s) was/were more likely to be concordant in localization (i.e., right/right or left/left localization) whereas, when the BN were solid, the coexisting thyroid nodule/nodules was/were more likely to be discordant. In women with cystic BNs (CBNs), TNs were more frequently multiple (64% of cases), whereas in cases with solid BNs (SBNs), the frequency of single and multiple TNs was approximately the same. In patients with TNs/CBNs, TNs tend to be subcentimetric and localized in the inferior pole of either thyroid lobe. In patients with TNs/SBNs, TNs tend to be larger and localized in the middle of either thyroid lobe. Conclusions: In women with BNs associated with TNs, there are interesting differences concerning TNs when patients are stratified based on the cystic or solid nature of the BN.