Tumor deposits in axillary adipose tissue in patients with breast cancer: Do they matter?

Tumor deposits (TDs) are defined as discrete, irregular clusters of tumor cells lying in the soft tissue adjacent to but separate from the primary tumor, and are usually found in the lymphatic drainage area of the primary tumor. By definition, no residual lymph node structure should be identified in these tumor masses. At present, TDs are mainly reported in colorectal cancer, with a few reports in gastric cancer. There are very few reports on breast cancer (BC). For TDs, current dominant theories suggest that these are the result of lymph node metastasis of the tumor with complete destruction of the lymph nodes by the tumor tissue. Even some pathologists classify a TD as two lymph node metastases for calculation. Some pathologists also believe that TDs belong to the category of disseminated metastasis. Therefore, regardless of the origin, TDs are an indicator of poor prognosis. Moreover, for BC, sentinel lymph node biopsy is generally used at present. Whether radical axillary lymph node dissection should be adopted for BC with TDs in axillary lymph nodes is still inconclusive. The present commentary of this clinical issue has certain guiding significance. It is aimed to increase the awareness of the scientific community towards this under-recognized problem in BC pathology.