# Two Cases of Distant Metastasis After Mastectomy for Breast Ductal Carcinoma In Situ

## TL;DR

This paper reports two rare cases where breast cancer that was initially non-invasive later spread to distant parts of the body after surgery.

## Contribution

The novelty lies in documenting two rare instances of distant metastasis following mastectomy for ductal carcinoma in situ with no local recurrence.

## Key findings

- Two patients with DCIS developed distant metastases despite negative surgical margins and sentinel nodes.
- Metastases occurred without prior invasive local recurrence in both cases.
- The study highlights the importance of informing patients about the rare risk of distant recurrence.

## Abstract

While the prognosis for ductal carcinoma in situ (DCIS) of the breast is generally excellent, distant metastasis after appropriate local treatment is extremely rare. We experienced two cases of distant metastasis after mastectomy for breast ductal carcinoma in situ. In both cases, the surgical margins were negative, the sentinel nodes were negative for metastasis. The first case was a 67-year-old woman who developed lung metastases four years after mastectomy for high-grade DCIS. The second case was a 34-year-old woman with intermediate-grade DCIS who developed intraductal recurrence localized to the nipple two years after the initial nipple-sparing mastectomy and multiple lung and liver metastases six months later. Both cases developed distant metastases despite appropriate local treatment, without preceding or concurrent invasive local recurrence. Although the probability of distant recurrence is low, it is important to inform patients about the risk of recurrence.