Background: The incidence of ductal carcinoma in situ (DCIS) has increased markedly with the introduction of population based mammographic screening. DCIS is usually diagnosed non-operatively. Although sentinel lymph node biopsy (SNB) has become standard of care in patients with invasive breast carcinoma the use of SNB in patients with DCIS is controversial.
Aims: This study examines the justification for offering SNB at the time of primary surgery to patients with a needle core biopsy (NCB) diagnosis of DCIS.
Methods: A retrospective analysis of 145 patients, diagnosed with DCIS by NCB and who had SNB performed at the time of primary surgery, was performed. The study focussed on rates of SNB positivity and underestimation of invasive carcinoma by NCB, and sought to identify factors that might predict the presence of invasive carcinoma in the excision specimen.
Results: 7/145 patients (4.8%) had a positive sentinel lymph node (SN), 4 macrometastases and 3 micrometastases. 6/7 patients had invasive carcinoma in the final excision specimen. 55/145 patients (37.9%) with NCB diagnosis of DCIS had invasive carcinoma in the excision specimen. The median invasive tumour size was 6mm. A radiological mass and areas of invasion less than 1mm, amounting to “at least microinvasion” on NCB were predictive of invasive carcinoma in the excision specimen.
Conclusions: SNB positivity in pure DCIS is rare. In view of the high rate of underestimation of invasive carcinoma in patients with NCB diagnosis of DCIS in this study, SNB appears justified in this group of patients in our centres.