Introduction
Skin-sparing mastectomy (SSM) with immediate breast reconstruction is the ideal treatment for interested and suitable patients with extensive ductal carcinoma in situ (DCIS). There is no guideline to indicate on how large DCIS the procedure can be performed safely. The primary target of this study was to define the oncological safety of SSM in extensive pure DCIS. The secondary target was to find predictive factors for DCIS upstaging to invasive disease.

Materials and methods
A total of 71 consecutive patients with extensive pure DCIS and undergoing SSM with immediate latissimus dorsi (LD) breast reconstruction were retrospectively evaluated.

Results
The median size of DCIS lesion in preoperative imaging was 60 mm, the median weight of mastectomy specimen was 350 g, and the median resection margin (RM) was 2.0 mm. A total of 20 patients (28%) had an RM less than 0.5 mm and nine patients (13%) had ink positive margins. Six patients having positive RM underwent reoperation. A total of 29 patients (41%) presented invasive cancer foci in final histopathological assessment and nine patients (13%) had an axillary metastasis. Adjuvant therapy was given to 23 patients presenting invasive cancer. There were no local recurrences or distant metastases (0%, 95% confidence interval 0-0.051) during the mean follow-up of 71 mo. None of the factors evaluated predicted upstaging to invasive disease.

Conclusions
SSM with immediate breast reconstruction in patients with extensive DCIS is oncologically safe even when the margins are close or positive. Additional invasive foci and solitary axillary lymph node metastases are frequent but do not worsen the outcome.