Definition

Axillary dissection is a surgical procedure that incises (opens) the armpit (axilla or axillary) to identify, examine, or remove lymph nodes (small glands, part of the lymphatic system, which filters cellular fluids).

Purpose

Axillary dissection is utilized to stage breast cancer in order to determine the necessity of further treatment based on cancer cell spread. Additionally, axillary dissection includes removal and pathological examination of axillary lymph nodes for persons having operable breast cancer. The anatomy of the axilla is complex and composed of several critical nerves, arteries, and muscles. Because of this complex anatomy and connection with the breast, the axilla is a common route for possible metastatic (cancer cell spread to distant areas within the body) involvement from breast cancer. The absence or presence of cancer cells in axillary lymph nodes is the most power prognostic (outcome) indicator for breast cancer. Axillary dissection is an accurate procedure for axillary node assessment (removal and pathological examination). Clinical examination of the breast (more specifically palpation, or feeling the affected area for lumps) for the axillary region is inaccurate and unreliable. The only method to identify whether or not a lymph node has cancer cells, is to surgically remove the node and perform examination with a microscope to detect abnormal cancer cells.

From http://www.healthline.com/galecontent/axillary-dissection