On average, 250 skin-sparing mastectomies with immediate prosthetic reconstruction are performed in the Dutch Antoni van Leeuwenhoek Hospital each year. We report on two breast cancer patients (46 and 53 years old) who each developed a local recurrence at the entry site of the core needle biopsy after skin-sparing mastectomy with immediate prosthetic reconstruction. In hindsight, the most likely cause for these recurrences was the fact that one of the entry sites for the core needle biopsies was not marked preoperatively, and thus not excised during surgery. These examples emphasise the need for accurate documentation of the locations of these entry sites, followed by their excision, in patients undergoing skin-sparing mastectomy for invasive breast cancer.