Abstract: Objective To analyze the clinical and pathological features of breast cancer in women under 35 years of age. Methods 153 breast cancer patients aged 35 or younger treated from Jan. 1, 2007 to Dec. 31, 2012 were retrospectively reviewed. The characteristics of breast cancer onset and clinical and pathological features in different molecular subtypes of breast cancer were analyzed by SPSS 17.0 statistics software. Results The most common symptom among young patients was breast lumps, and 107 (69.9%) of the patients went to the hospital within six months as soon as the symptom was appeared. Among these 153 samples, 22 (14.4%) were diagnosed as having ductal carcinomas in situ, and 131 (85.6%) had invasive cancers. In addition, based on immunohistochemistry, the invasive cancers were categorized into four molecular subtypes: luminal A (30, 22.9%), luminal B (65, 49.7%), Her-2 over-expression (18, 13.7%) and basal-like (18, 13.7%). The most invasive cancers were in histological grades Ⅱ (76, 58.0%) and Ⅲ (2, 24.4%). In luminal A subtype, the diameter≤2 cm and histological grade Ⅰ ranked higher than in any other subtypes. There were no significant differences among different subtypes regarding lymph node metastasisand clinical stage. The invasive cancers had a high positive rate of Ki67, with an average of (30.12±3.91)%. Conclusion The clinical stages of young breast cancer patients are more advanced; tumor diameter and histological grade are closely related with molecular subtypes; the high positive rate of Ki67 and the high proportion of the molecular subtypes with adverse prognosis imply poor prognosis. We should pay more attention on the early diagnosis of young patients.

Key words: Breast tumor, Pathological features, Young women, Clinical features, Molecular subtypes