Hormonal and Reproductive Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD, USA.
Acta Paediatr. 2011 Jun;100(6):814-8. doi: 10.1111/j.1651-2227.2010.02131.x. Epub 2011 Jan 18.
To evaluate male breast cancer (MBC) risk among patients with Klinefelter syndrome (KS) and relate this to possible biological explanations.
A literature review was conducted to identify case series and epidemiologic studies that have evaluated MBC risk among patients with KS.
Case reports without expected values have often led to false impressions of risk. Problems include that a diagnosis of cancer can prompt a karyotypic evaluation and that many cases of KS are unrecognized, resulting in incomplete denominators. Few carefully conducted epidemiologic studies have been undertaken given that both KS and MBC are rare events. The largest study found 19.2- and 57.8-fold increases in incidence and mortality, respectively, with particularly high risks among 47,XXY mosaics. These risks were still approximately 70% lower than among females, contradicting case reports that patients with KS have breast cancer rates similar to females. Altered hormone levels (especially the ratio of oestrogens to androgens), administration of exogenous androgens, gynaecomastia and genetic factors have been offered as possible explanations for the high risks.
Additional well-designed epidemiologic studies are needed to clarify which patients with KS are at a high risk of developing MBC and to distinguish between possible predisposing factors, including altered endogenous hormones.
评估克氏综合征（KS）患者的男性乳腺癌（MBC）风险，并探讨可能的生物学解释。
进行文献回顾，以确定评估 KS 患者 MBC 风险的病例系列和流行病学研究。
缺乏预期值的病例报告常常导致风险的错误印象。存在的问题包括癌症诊断可能促使进行核型评估，而且许多 KS 病例未被识别，导致分母不完整。由于 KS 和 MBC 均为罕见事件，因此很少进行精心设计的流行病学研究。最大的一项研究发现，MBC 的发病率和死亡率分别增加了 19.2 倍和 57.8 倍，尤其是 47,XXY 嵌合体的风险更高。这些风险仍比女性低约 70%，与患者 KS 乳腺癌发病率与女性相似的病例报告相矛盾。改变的激素水平（尤其是雌激素与雄激素的比值）、外源性雄激素的使用、男性乳房发育症和遗传因素被认为是高风险的可能解释。
需要更多设计良好的流行病学研究来阐明哪些 KS 患者有发生 MBC 的高风险，并区分可能的易感因素，包括改变的内源性激素。
