Sentinel lymph node metastasis from mammary ductal carcinoma in situ with microinvasion.

Axillary lymph node dissection (ALND) in patients with ductal carcinoma in situ with microinvasion (DCISM) of the breast was controversial, because of the relevant morbidity incurred by the procedure and the low incidence of axillary involvement. The introduction of the sentinel lymph node (SLN) biopsy as a minimally invasive procedure for axillary staging has prompted new interest in this issue. However, as DCISM is a rare type of cancer, data on the incidence of SLN metastasis are scarce. The aim of the present paper was therefore to assess the prevalence of SLN metastasis in a multi-institutional series of DCISM patients, in order to ascertain whether SLN biopsy might be justified as a standard procedure in the presence of microinvasive cancer. Between 1999 and 2004, 43 patients with a diagnosis of DCISM underwent SLN biopsy. Microinvasion was defined as one or more foci of invasion beyond the basal membrane, none exceeding 1mm. SLNs were examined following haematoxylin-eosin and immunohistochemical staining. SLN metastases were found in four out of 43 cases (9.3%). In one patient, SLN contained only micrometastasis. All four patients with positive SLN underwent complete ALND and in all these cases further metastatic axillary nodes were found. In conclusion, given the relevant incidence of nodal metastases and the low morbidity of the procedure, we believe that SLN biopsy should be considered in all patients with a diagnosis of DCISM. In cases of SLN involvement, even if micrometastatic, our policy is to perform a complete ALND.