**1. Introduction**

Colon cancer is a frequent neoplastic disease which is ranked second in female after breast cancer and third in men after prostate and lung and cancer [1]. Despite constant research in the field of colon cancer, its incidence continues to be high worldwide. Moreover, the number of people age 50 or younger diagnosed with colon cancer is dramatically increasing in last years. This finding upholds the idea that colon cancer is not a disease considered to be under control at this time, and efforts should be made in order to better understand its pathogenic mechanism.

Five-year overall survival in colon cancer ranges from 90% in early stages to less than 10% in advanced, metastatic cases [2]. It is thus important to try to diagnose the disease in early stage, so an appropriate treatment can be applied. Achieving this condition can be difficult, considering the fact that a large number of colon cancer patients present with late stage, often inoperable tumors.

Even if important progress has been made in terms of imaging diagnosis of colon cancer, early detection is still difficult to achieve. An important role in detecting early colon cancer cases is assigned to screening programs that have to be applied nationally, and population should be well informed of their importance. More than detecting incipient cases, early detection of advanced cases is also of crucial importance, and efforts should continue in this direction by further research groups.

Colon cancer stem cells (CCSCs) are multipotent neoplastic cells that have the ability to differentiate and initiate the carcinogenesis process [3]. Due to their increased viability, CCSCs are responsible for both tumor growth and tumor recurrence [4, 5]. According to a recent study, the presence of CCSCs is also responsible for resistance to chemotherapeutic treatments, which is observed in some cases [5]. A new treatment concept linked to CCSCs is based on their early detection, before the onset of the tumor, which would allow them to target with apoptotic substances.

Detection of cancer stem cells (CSCs) in various digestive and extra-digestive cancers has been a topic of great interest in the literature of recent years and was frequently done using cluster of differentiation (CD) markers. In colon cancer, various biomarkers have been identified at the surface of CSCs, and their role in colon cancer is currently being tested: EpCAM, CD133, CD29, CD24, CD44, CD166, ALDH1A1, and ALDH1B1 [3, 4].

The aim of this paper is to review the most important biomarkers which have been identified in colon cancer, to expose current information regarding their role in colon cancer development and progression and to identify possible predictive biomarkers for advanced stages of the disease.
