What happened, in summary

A 60-year-old woman was diagnosed in 2017 with an early right invasive ductal breast cancer. She underwent lumpectomy and sentinel lymph-node biopsy. The 35 mm tumor was estrogen-receptor positive, progesterone-receptor positive, and HER2-negative, with no involved sentinel nodes. She declined recommended radiation and endocrine therapy and instead used subcutaneous mistletoe extract. Almost 3 years later, a 7 mm local recurrence was confirmed in the same breast. The recurrent tumor remained strongly estrogen-receptor positive and HER2-negative but was progesterone-receptor negative. She again declined surgery, radiation, and endocrine therapy at that point and continued mistletoe extract. Four months after the recurrence was diagnosed, she received a one-time intravenous mistletoe dose together with intratumoral mistletoe extract and an intratumoral influenza-vaccine injection. Follow-up ultrasound in March 2021 could no longer identify the recurrent lesion. She later agreed to lumpectomy in May 2021. Pathology found only a 1 mm residual focus, described as a near-complete pathologic response. At the latest follow-up in the case report, she remained in remission 3 years after surgery for the recurrence.