Breast cancer in young (<40 years) is associated with a higher frequency of aggressive tumor types and poor prognosis. It remains unclear if there is an underlying age-related biology that contributes to the unfavorable outcome. We aim to investigate the relationship between age and breast cancer biology, with emphasis on proliferation. Clinico-pathologic information, immunohistochemical markers and follow-up data were obtained for all patients aged <50 (Bergen cohort-1; n = 355, not part of a breast screening program) and compared to previously obtained information on patients aged 50 to 69 years (Bergen cohort-2; n = 540), who participated in the Norwegian Breast Cancer Screening Program. Young breast cancer patients presented more aggressive tumor features such as hormone receptor negativity, HER2 positivity, lymph-node metastasis, the HER2-enriched and triple-negative subtypes and shorter survival. Age <40 was significantly associated with higher proliferation (by Ki67). Ki67 showed weaker prognostic value in young patients. We point to aggressive phenotypes and increased tumor cell proliferation in breast cancer of the young. Hence, tumors of young breast cancer patients may present unique biological features, also when accounting for screen/interval differences, that may open for new clinical opportunities, stratifying treatment by age.

中文翻译：

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乳腺癌的年龄相关表型：一项基于人群的研究

年轻（<40 岁）的乳腺癌与侵袭性肿瘤类型的发生率较高和预后不良有关。目前尚不清楚是否存在与年龄相关的潜在生物学因素导致不良结果。我们的目标是研究年龄与乳腺癌生物学之间的关系，重点是增殖。获得了所有年龄 <50 岁患者（Bergen 队列 1；n = 355，不属于乳腺筛查计划的一部分）的临床病理信息、免疫组织化学标记物和随访数据，并与之前获得的 50 至 69 岁患者的信息进行了比较年（卑尔根队列 2；n = 540），参加了挪威乳腺癌筛查计划。年轻乳腺癌患者表现出更具侵袭性的肿瘤特征，例如激素受体阴性、HER2阳性、淋巴结转移、HER2富集和三阴性亚型以及较短的生存期。年龄 <40 岁与较高的增殖显着相关（通过 Ki67）。 Ki67 在年轻患者中显示出较弱的预后价值。我们指出年轻乳腺癌的侵袭性表型和肿瘤细胞增殖增加。因此，年轻乳腺癌患者的肿瘤可能呈现出独特的生物学特征，同时考虑到筛查/间隔差异，这可能会带来新的临床机会，按年龄分层治疗。