The relationship between breast cancer (BC) and thyroid disease (TD) is still controversial. The aim of the study was to investigate the possible coexistence of TD in patients with newly diagnosed BC and its correlation with BC clinical presentation with regard to menopausal status and stage of disease. This is a retrospective cohort study of all patients treated for primary BC between 2014 and 2016 at the Breast Unit of Trieste University Hospital. Clinical charts and reports were reviewed for coexisting thyroid disorders (i.e. hyperthyroidism, hypothyroidism, benign TD, thyroid cancer, thyroid autoimmunity) and menopausal status at the time of BC diagnosis. Biomolecular profile, stage, and grading of BC were also evaluated. A total of 786 women and 7 men were included in the study. Co-presence of TD was found in 161(20.3%) cases: of these, 151(19.4%) patients presented benign TD and 10(1.3%) patients presented thyroid carcinoma. Thyroid autoimmunity was found in 51(32%) patients. Regarding thyroid function, 88(55%) patients had hypothyroidism, 19(12%) hyperthyroidism, and 54(33%) normal thyroid function. No statistically significant correlation was found between age and TD (p = 0.16), although TD was more common in women aged ≥60 years. Women with BC diagnosed at pre-menopausal age were more likely to have thyroid autoimmune diseases (45% vs. 29%, p = 0.05). No association was detected among BC molecular profiles with either thyroid autoimmunity (p = 0.26) or altered thyroid function (p = 0.63). High-grade BC was more frequent in women with hyperthyroidism (52.9%, p = 0.04), but the grading was independent from the presence of thyroid autoimmune disease (p = 0.87). BC stage was related to both thyroid autoimmunity (p = 0.04) and thyroid function (p < 0.001), with 55.2% of women affected by benign TD presenting with stage I BC and more aggressive BCs found in hypothyroid patients. According our study results, patients with primary BC present a greater incidence of autoimmunity disorders, especially when diagnosed in the pre-menopausal setting. However, further prospective studies are required to definitively prove causality.

中文翻译：

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甲状腺良性疾病与乳腺癌之间的关联：单中心经验

乳腺癌（BC）和甲状腺疾病（TD）之间的关系仍存在争议。这项研究的目的是研究绝经状态和疾病分期在新诊断的BC患者中可能存在TD及其与BC临床表现的相关性。这是对2014年至2016年在的里雅斯特大学医院乳腺科接受原发性BC治疗的所有患者的回顾性队列研究。在进行BC诊断时，对临床图表和报告进行了共存甲状腺疾病（即甲状腺功能亢进，甲状腺功能减退，良性TD，甲状腺癌，甲状腺自身免疫性疾病）和绝经状态的回顾。还评估了生物分子谱，BC的阶段和等级。该研究总共包括786名女性和7名男性。在161（20.3％）例病例中发现TD并存：151例（19.4％）患者表现为良性TD，10例（1.3％）患者表现为甲状腺癌。51（32％）患者发现甲状腺自身免疫。在甲状腺功能方面，有88（55％）的患者甲状腺功能减退，19（12％）甲状腺功能亢进和54（33％）甲状腺功能正常。尽管TD在60岁以上的女性中更为常见，但在年龄和TD之间没有统计学上的显着相关性（p = 0.16）。在绝经前年龄被诊断为BC的女性更容易患甲状腺自身免疫性疾病（45％比29％，p = 0.05）。在BC分子图谱中未发现与甲状腺自身免疫性疾病（p = 0.26）或甲状腺功能改变（p = 0.63）相关。甲状腺机能亢进妇女中高等级BC更为常见（52.9％，p = 0.04），但分级与甲状腺自身免疫性疾病的存在无关（p = 0.87）。BC期与甲状腺自身免疫（p = 0.04）和甲状腺功能（p <0.001）有关，受良性TD影响的55.2％的女性表现为I期BC，甲状腺功能减退患者中发现更具侵略性的BC。根据我们的研究结果，原发性BC患者表现出更高的自身免疫性疾病发生率，尤其是在绝经前进行诊断时。但是，需要进一步的前瞻性研究来确定因果关系。