Importance of the retro-mammary space as a route of breast cancer metastasis

Abstract

Background

There are many cases of breast cancer with axillary lymph node metastases without lymphatic invasion. We hypothesized that in these cases cancer cells may pass through the retro-mammary space (RS) into lymph nodes and that axillary lymph node metastases may correlate with the tumor invasion of the RS.

Methods

A total of 127 patients who had undergone radical operation between April 1997 and April 2001 were studied. Whether or not the tumor had invaded the RS was histologically examined with hematoxylin and eosin staining of sections made at the point where the distance between the tumor and the fascia of the major pectoral muscle was the shortest.

Results

Eighty-five cases did not have lymphatic invasion. Twenty-nine of these 85 cases had RS invasion and 56 cases did not. Among the 29 cases with RS invasion, 14 cases had lymph node metastases. In contrast, of 56 cases without RS invasion only 3 cases had lymph node involvement. Of the 85 cases without lymphatic invasion, the relationship between RS invasion and lymph node invasion was statistically significant (RS(+) vs. RS(-),p < 0.0001,X ² test). For all 127 cases, if cases showing either lymphatic invasion or RS invasion were diagnosed with lymph node involvement, the sensitivity, specificity, accuracy, and negative predictive value were 93.5%, 65.4%, 75.6% and 94.6%, respectively.

Conclusion

These data suggest that lymph node metastases may occur via the tumor cell migration through lymphatic vessels and the RS.