A 37-Year Retrospective Analysis Reveals a High Rate of Cutaneous Angiosarcoma of the Scalp in Okinawa, Japan

Angiosarcoma (AS) is a rare, aggressive malignancy originating from vascular or lymphatic endothelial cells. Despite its severity, little is known about its epidemiology, and no geographical regions have previously been identified as having an exceptionally high incidence. We retrospectively analyzed medical records spanning 37 years (1987-2023) in Okinawa, Japan, identifying 135 cases of AS that were used to calculate its incidence. This incidence was compared to global data to highlight significant regional differences. Factors related to patients' survival were also assessed. The age-adjusted incidence of AS of the scalp in Okinawa was 4.1 per million per year (mpy; 2015 Japanese model population) or 2.0 per mpy (2000 US standard population), significantly higher than the global data, including in the United States (about eightfold higher) and mainland Japan (about fourfold higher). The estimated five-year survival for patients with AS of the scalp in Okinawa was 9.2%. Multivariate analysis identified surgery, chemotherapy, and radiotherapy as significant factors associated with patient survival. This study provides the first evidence of a significantly higher incidence rate of AS of the scalp in Okinawa. Given its rarity, further research is crucial to uncover the epidemiological, genetic, and environmental factors driving this cancer.