Modes of benign mechanical transport of breast epithelial cells to axillary lymph nodes.

The status of axillary lymph nodes is a key prognostic indicator available for the management of patients with breast cancer. Sentinel lymph node (SLN) evaluation as a predictor of lymph node status has led to increased use of ancillary methods, principally immunohistochemistry, to increase the sensitivity of the SLN biopsy. So-called "occult" micrometastases detected by such methods have led to speculation that some may have reached the SLNs by benign mechanical transport (BMT) rather than a metastatic process. We review evidence suggesting two potential modes of BMT: lymphatic transport of epithelial cells displaced by biopsy of the primary breast tumor and by breast massage-assisted SLN localization. The biopsy techniques under most scrutiny include fine needle aspiration and large-gauge core biopsy. The evidence implicating breast massage prior to SLN biopsy as a mode of BMT has been supported by statistical analysis; however, no method of distinguishing massage-associated cells in SLNs from true occult micrometastases is available. The significance of small epithelial clusters in SLNs is currently unknown. Thus, deviation from current biopsy and SLN-localizing practices is unwarranted.

Benign mechanical transport of breast epithelial cells to sentinel lymph nodes.

The evaluation of sentinel lymph nodes (SLNs) for the presence of malignant epithelial cells is essential to the staging of breast cancer patients. Recently, increased attention has focused on the possibility that epithelial cells may reach SLNs by benign mechanical means, rather than by metastasis. The purpose of this study was to test the hypothesis that pre-SLN biopsy breast massage, which we currently use to facilitate the localization of SLNs, might represent a mode of benign mechanical transport. We studied 56 patients with invasive and/or in situ ductal carcinoma and axillary SLNs with only epithelial cells and/or cell clusters (< or =0.2 mm in diameter and not associated with features of established metastases) detected predominantly in subcapsular sinuses of SLNs on hematoxylin and eosin- and/or anti-cytokeratin-stained sections. No patient had an SLN involved by either micro- or macro-metastatic carcinoma. Epithelial cells and cell clusters, < or =0.2 mm in size and without features of established metastases, occurred more frequently in the SLNs of patients who underwent pre-SLN biopsy breast massage (P < 0.001, chi2 test). The latter finding supports the hypothesis that pre-SLN biopsy breast massage is a mode of benign mechanical transport of epithelial cells to SLNs.