[Axillary lymph node and bone marrow micrometastases of breast cancer]

Micrometastatic disease from breast cancer is a major concern both for clinicians and pathologists. Histologically, they can be defined as potentially invasive microfoci of tumoral cancer cells located in the vicinity of blood vessels and are a distinct entity from residual disease. They are mainly looked for in bone marrow and lymph nodes specimens and their diagnosis is currently easier thanks to immunohistochemistry. Provided a standard definition of micrometastatic disease and standard screening procedures can be met, the presence of micrometastases at the time of diagnosis could represent a major parameter in therapeutic decision-making. Although controversial, the presence of medullary and axillary lymph node micrometastases appears to be a major prognostic factor in terms of survival. Recognition of this entity could help in better defining the high-risk subset of patients who would potentially benefit from adjuvant chemotherapy.