Sentinel lymph node metastasis in microinvasive breast cancer.

Background: Ductal carcinoma in situ with microinvasion (DCISM) is a separate pathological entity, distinct from pure ductal carcinoma in situ (DCIS). DCISM is a true invasive breast carcinoma with a well-known metastatic potential. Currently, there is controversy regarding the indication for complete axillary dissection (CAD) to stage the axilla in patients with DCISM. The role of CAD is questioned given its morbidity and reported low incidence of axillary involvement. Sentinel lymph node biopsy (SLNB) may obviate the need for CAD in these patients without compromising the staging of the axilla and the important prognostic information.

Methods: From March 1996 to December 2002, 4602 consecutive patients with invasive breast carcinoma underwent SLN biopsy. Of these, 41 patients with DCISM were selected.

Results: Metastasis in the SLN were detected in 4 of 41 (9.7%) patients. Two of the 4 patients had only micrometastasis in the SLN. In three patients, the SLN was the only positive node after CAD.

Conclusions: SLN biopsy should be considered as a standard procedure in DCISM patients. SLNB can detect nodal micrometastasis and accurately stage the axilla avoiding the morbidity of a CAD. Complete AD may not be mandatory if only the SLN contains micrometastatic disease. Informed consent is very important in the decision not to undergo CAD.