Recent technological advances have led to an increasing ability to detect isolated or groups of tumour cells in blood, lymph nodes or bone marrow in patients with different tumour types. However, the clinical evidence of these advances is unclear. The detection and the characterisation of circulating breast cancer cells and the eventually micrometastasis represent an important prognostic factor with therapeutic implications. The number of neoplastic cells being very small, these are not easily detected by using only cytomorphology, possibly associated to immunocytochemistry. In the last decade many studies have been directed in order to identify new assays. In the present review the Authors summarize advantages and disadvantages about two different technical approaches: molecular and immunomagnetic selection with cellular enrichment and immunocytochemistry.