Upstaging to invasive ductal carcinoma after mastectomy for ductal carcinoma in situ: predictive factors and role of sentinel lymph node biopsy

The aim of this study was to investigate preoperative factors associated with ductal carcinoma in situ (DCIS) upstaged to invasive ductal carcinoma (IDC) and sentinel lymph node (SLN) status in patients who underwent mastectomy for a preoperative diagnosis of DCIS. The medical records of 220 patients who underwent mastectomy for a preoperative diagnosis of DCIS were retrospectively reviewed. Fifty-one (22.6%) of 226 lesions were upgraded to IDC after mastectomy. Preoperative factors associated with upstaging to IDC included patient-reported signs and symptoms, a clinically palpable mass, ultrasound findings classified as category 4 or 5, the ultrasound appearance of a mass or widely distributed non-mass abnormality (NMA), and a high Ki67 index. The prevalence of SLN macrometastasis was 0.9%. IDC was diagnosed for 10.9% of lesions of a preoperative ultrasound category of 0–3, 13.0% of those with no mass or NMA detected by ultrasonography, and 14.1% of lesions preoperatively diagnosed by methods other than core needle biopsy (CNB). Of those lesions, none was associated with SLN metastasis. Routinely performing SLN biopsy for patients undergoing mastectomy for a preoperative diagnosis of DCIS is overtreatment, because the prevalence of SLN metastasis was low. SLN biopsy can be omitted for most patients. In particular, we suggest omitting SLN biopsy for patients who have lesions of ultrasound category 0–3, who have neither a mass nor NMA detected by ultrasound, or whose initial diagnosis was made based on a specimen obtained by methods other than CNB.