The important challenge about cancer is diagnosis in primary stages and proper treatment. Although classical clinico-pathological features of the tumor have major prognostic value, the advances in diagnosis and treatment are indebted to discovery of molecular biomarkers and control of cancer in the pre-invasive state. Moreover, the efficiency of available therapeutic options is highly diminished, and chemotherapy is still the main treatment due to lack of enough specific targets. Accordingly, finding the new noninvasive biomarkers for cancer is still an important clinical challenge that is not achieved yet. There are current technologies to screen, diagnose, prognose, and treat cancer, but the limitations of these implements and procedures are undeniable. Liquid biopsy as a noninvasive method has a promising future in the field of cancer, and exosomes as one of the recent areas have drawn much attention. In this review, the potential capability of exosomes is summarized in cancer with the special focus on breast cancer as the second cause of cancer mortality in women all around the world. It discusses reasons to choose exosomes for liquid biopsy and the studies related to different potential biomarkers found in the exosomes. Moreover, exosome studies on milk as a specific biofluid are also discussed. At last, because choosing the method for exosome studies is very challenging, a summary of different techniques is provided.

癌症的重要挑战是初级阶段的诊断和适当的治疗。尽管肿瘤的经典临床病理特征具有重要的预后价值，但诊断和治疗的进步归功于分子生物标志物的发现以及在侵袭前状态下对癌症的控制。此外，现有治疗方案的效率大大降低，由于缺乏足够的特异性靶点，化疗仍然是主要治疗方法。因此，寻找新的癌症非侵入性生物标志物仍然是尚未实现的重要临床挑战。目前有用于筛查、诊断、预测和治疗癌症的技术，但这些工具和程序的局限性是不可否认的。液体活检作为一种非侵入性方法在癌症领域有着广阔的前景，而外泌体作为近年来备受关注的领域之一。在这篇综述中，总结了外泌体在癌症中的潜在能力，特别关注乳腺癌作为全世界女性癌症死亡的第二大原因。它讨论了选择外泌体进行液体活检的原因以及与外泌体中发现的不同潜在生物标志物相关的研究。此外，还讨论了关于牛奶作为特定生物流体的外泌体研究。最后，由于选择外泌体研究的方法非常具有挑战性，因此总结了不同的技术。