Visceral Angiosarcoma: A Nationwide Population-Based Study from 2000-2017.

: Angiosarcomas arise from vascular or lymphatic endothelial cells and can develop at any site. Visceral angiosarcomas are aggressive high-grade tumors with a high risk of recurrence, metastasis, and poor survival. Nationwide studies with long-term follow-up are limited, but crucial for understanding this malignancy. This study aimed to describe a national cohort of patients with visceral angiosarcomas and estimate long-term survival, local recurrence, and metastases. : We included all adult patients in Denmark diagnosed with histologically confirmed visceral angiosarcoma from 2000 to 2017. Data were obtained from the Danish Pathology Register and the Danish Sarcoma Database, both providing nationwide and comprehensive records. Additional information on demographics, comorbidities, symptoms, diagnosis, tumor location, treatment, recurrence, and survival were collected from registries and health records. : Eighteen patients with visceral angiosarcoma were identified, corresponding to an incidence of one per 5.5 million inhabitants per year. The median age was 56.5 years (IQR: 50-70), and 56% were female. Tumors were most commonly located in the kidney, liver, and thoracic wall. Metastases were present at diagnosis in 17% and developed later in 50%. Surgery was performed in 61%, with R0 resection in 55%. Median overall survival was 249 days (IQR: 121-858), and the 5-year survival rate was 11%. Only one patient (6%) remained alive at long-term follow-up. : This Danish nationwide study confirms that visceral angiosarcomas are rare, highly aggressive tumors with a poor prognosis, consistent with international findings. Despite the small cohort, the disease demonstrated significant heterogeneity in anatomical location, metastatic pattern, and treatment approaches.