浸润性导管癌 (IDC) 和浸润性小叶癌 (ILC) 之间不同的预后意义已得到证实。然而，有关绝经前患者的信息仍然不足。使用国家数据库检查绝经前患者 ILC 和 IDC 的长期生存结果。这项队列研究使用了韩国乳腺癌登记处 (KBCR) 的监测、流行病学和最终结果 (SEER)和峨山医疗中心研究 (AMCR) 数据库，以确定 1990 年 1 月 1 日至 2015 年 12 月 31 日期间患有 I 至 III 期 ILC 或 IDC 的绝经前患者。中位随访时间为 90 (IQR，40-151) 个月在 SEER 数据库中，在 KBCR 数据库中为 94（IQR，65-131）个月，在 AMCR 数据库中为 120（IQR，86-164）个月。数据分析时间为2023年1月1日至5月31日。主要结局为乳腺癌特异性生存率（BCSS），根据组织学类型进行分析，并评估年度风险率。使用对数秩检验和具有时变系数的 Cox 比例风险回归模型来分析生存率。通过调整肿瘤特征和治疗因素进行多变量分析。共确定了 225938 名诊断为 IDC 或 ILC 且年龄小于 50 岁的女性。 SEER 数据库中诊断时的平均 (SD) 年龄为 42.7(5.3) 岁，KBCR 数据库中为 41.8(5.5) 岁，AMCR 数据库中为 41.8(5.5) 岁。就种族而言（仅适用于 SEER 数据库），12.4% 的患者为黑人，76.1% 为白人，11.0% 为其他种族（包括美洲印第安人或阿拉斯加原住民、亚洲人、夏威夷原住民或其他太平洋岛民）， 0.5% 为未知种族）。 ILC 患者在诊断后的前 10 年中比 IDC 患者具有更好的 BCSS（SEER 数据库中的风险比 [HRs]，0.73 [95% CI，0.68-0.78]，2017 年的风险比 [HRs]，1.20 [95% CI，0.91-1.58] KBCR 数据库中为 0.50 [95% CI，0.29-0.86]），尽管 BCSS 在 10 年后更差（SEER 数据库中为 1.80 [95% CI，1.59-2.02]，2.79 [95% CI） KBCR 数据库中的 CI，1.32-5.88]，AMCR 数据库中的 2.23 [95% CI，1.04-4.79]）。激素受体阳性肿瘤也观察到类似的趋势（SEER 数据库中的 HR 为 1.55 [95% CI，1.37-1.75]，KBCR 数据库中的 HR 为 2.27 [95% CI，1.01-5.10]，以及 2.12 [95% CI， 0.98-4.60] AMCR 数据库中）。考虑到 BCSS 的年度风险模型，IDC 事件在诊断前 5 年达到峰值后趋于稳定下降。然而，在诊断 ILC 后 5 年观察到 BCSS 的年度峰值事件，随后保持不变。这些发现表明，患有 ILC 的绝经前女性的 BCSS 估计值比 IDC 的女性差，这可归因于 ILC 的晚期复发率较高。 ILC 优于 IDC。在确定绝经前女性内分泌治疗的类型和持续时间时，应考虑组织学亚型。

The disparate prognostic implications between invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) have been demonstrated. However, information on premenopausal patients remains insufficient.To examine long-term survival outcomes of ILC and IDC in premenopausal patients using national databases.This cohort study used the Surveillance, Epidemiology, and End Results (SEER), Korean Breast Cancer Registry (KBCR), and Asan Medical Center Research (AMCR) databases to identify premenopausal patients with stage I to III ILC or IDC between January 1, 1990, and December 31, 2015. The median follow-up time was 90 (IQR, 40-151) months in the SEER database, 94 (IQR, 65-131) months in the KBCR database, and 120 (IQR, 86-164) months in the AMCR database. Data were analyzed from January 1 to May 31, 2023.The primary outcome was breast cancer-specific survival (BCSS), which was analyzed according to histological type, and the annual hazard rate was evaluated. Survival rates were analyzed using a log-rank test and a Cox proportional hazards regression model with time-varying coefficients. Multivariable analysis was performed by adjusting for tumor characteristics and treatment factors.A total of 225 938 women diagnosed with IDC or ILC and younger than 50 years were identified. Mean (SD) age at diagnosis was 42.7 (5.3) years in the SEER database, 41.8 (5.5) years in the KBCR database, and 41.8 (5.5) years in the AMCR database. In terms of race (available for the SEER database only), 12.4% of patients were Black, 76.1% were White, 11.0% were of other race (including American Indian or Alaska Native, Asian, and Native Hawaiian or Other Pacific Islander), and 0.5% were of unknown race). Patients with ILC had better BCSS in the first 10 years after diagnosis than those with IDC (hazard ratios [HRs], 0.73 [95% CI, 0.68-0.78] in the SEER database, 1.20 [95% CI, 0.91-1.58] in the KBCR database, and 0.50 [95% CI, 0.29-0.86] in the AMCR database), although BCSS was worse after year 10 (HRs, 1.80 [95% CI, 1.59-2.02] in the SEER database, 2.79 [95% CI, 1.32-5.88] in the KBCR database, and 2.23 [95% CI, 1.04-4.79] in the AMCR database). Similar trends were observed for hormone receptor-positive tumors (HRs, 1.55 [95% CI, 1.37-1.75] in the SEER database, 2.27 [95% CI, 1.01-5.10] in the KBCR database, and 2.12 [95% CI, 0.98-4.60] in the AMCR database). Considering the annual hazard model of BCSS, IDC events tended to decline steadily after peaking 5 years before diagnosis. However, the annual peak event of BCSS was observed 5 years after diagnosis for ILC, which subsequently remained constant.These findings suggest that premenopausal women with ILC have worse BCSS estimates than those with IDC, which can be attributed to a higher late recurrence rate of ILC than that of IDC. Histological subtypes should be considered when determining the type and duration of endocrine therapy in premenopausal women.