Basile Pache, Antonia Digklia*, Nicolas Demartines, Maurice Matter. When lymph node metastases of breast carcinoma meet lymph node metastases of a radio-induced angiosarcoma Basile Pache, Antonia Digklia*, Nicolas Demartines, Maurice Matter. Department of Visceral Surgery, *Department of Oncology, Lausanne University Hospital CHUV , Switzerland. Introduction Radio-induced angiosarcoma is a rare aggressive soft tissue sarcoma. Lymph node metastatic risk is considered low and radical lymph node dissection (RLND) is generally not recommended. We present a case with very atypical behavior. Case report A 72 year-old woman had a past medical history of invasive ductal carcinoma of the left breast in 2008. Tumorectomy and axillary RLND were performed (pT1c pN1 (1sn/22) cM0), followed by chemotherapy, radiotherapy (66 Gy) and adjuvant hormonal therapy. Evolution was uneventful with complete remission until 2015, when a skin lesion of the left breast was identified as an angiosarcoma. A CT-scan disclosed a left pectoral mass (Fig. 1) together with a right axillary enlarged lymph node (FNA biopsy negative). Radical left mastectomy was first performed and disclosed a grade II angiosarcoma (pT2 NX MX). Resection was marginal. Three months later, chest MRI displayed local recurrence, and thoraco-abdominal CT-scan showed lung metastasis, motivating Paclitaxel therapy. Ultrasound examination showed a stable right axillary lymph node. Following multidisciplinary re-assessment, a left thoracic wall resection was perrfomed 3 months later (en bloc with pectoralis muscles) with mesh and latissimus dorsi reconstruction and new exploration of the left axillary area. Surprisingly, there was a double metastatic disease (Fig. 2) with lymph nodes displaying angiosarcoma (1/6 nodes) and ductal carcinoma of the breast (2/6 nodes). No residual angiosarcoma in the chest wall. One month later a thoraco-abdominal CT-scan showed an enlarging right axillary lymph node: FNA was positive for angiosarcoma . Consecutive right axillary RLND disclosed 1/12 metastatic lymph node for angiosarcoma. As of today, the patient is in remission. Fig 1 : 7 years after 66 Gy of radiotherapy, a mass appears in the breast. Fig 2 : 7 months after Fig.1 left axillary lymph node reveal metastasis of both angiosarcoma and ductal breast carcinoma Findings in literature Radio-induced angiosarcoma has a growing incidence possibly due to adjuvant radiotherapy in breast conservative surgery (cumulative incidence of 0.9 per 1000 cases during 15 years)1, with a time from radiation therapy to diagnosis of 7 years in average. Breast angiosarcoma seems to have a better prognosis compared to other primary sites, justifying aggressive surgery2. Modification of lymphatic network is a well known consequence of surgery, RLND or radiotherapy Conclusion - This patient is an example of a shift from the left to the right contro-lateral side of lymphatic drainage and risk of lymphatic metastasis. Lymph node metastatic risk in breast angiosarcoma is low but not zero 2-3. Lymphatic basins should be controlled during follow-up, and surgery performed accordingly. - There is a lack of consensus in the management of diagnosis, treatment and follow-up of angiosarcomas, studies are needed further. References Lucas. Arch Pathol Lab Med. 2009(11);133:1804–1809. Fayette J et al. Ann Oncol 2007;18: 2030. Stolnicua S et al. Ann Pathol 2015, 35 : 15. Contact basile.pache@chuv.ch