Secondary Publication of Japanese Dermatological Association Guidelines: Clinical Questions of Guidelines for Cutaneous Angiosarcoma 2025.

Cutaneous angiosarcoma is a rare aggressive malignancy with poor prognosis. Due to its rarity, high-level evidence from randomized controlled trials is limited, and treatment strategies have historically been adapted from other sarcomas. These guidelines aim to provide updated recommendations based on newly available evidence to standardize clinical practice in Japan. The 2024 revision was conducted under the Japanese Dermatological Association's commission, incorporating expert reviews and public comments. Given the lack of an established staging system, recommendations were formulated through systematic literature reviews and a structured consensus process. Five clinical questions were addressed, covering first-line chemoradiotherapy (CRT), management of residual lesions post-CRT, second-line treatment options, the role of pembrolizumab in tumor mutational burden-high cases, and treatment strategies for nonhead-and-neck angiosarcomas. Key recommendations include weakly recommending CRT for large (≥ 5 cm) nonmetastatic tumors, preferring drug modification over excision for residual lesions after CRT, and equally considering docetaxel, pazopanib, or eribulin for paclitaxel-resistant cases. Pembrolizumab was weakly recommended for tumor mutational burden-high cases. For radiation-associated angiosarcoma, surgical treatment was favored over CRT, while Stewart-Treves syndrome cases were treated similarly to head-and-neck angiosarcoma. Future directions emphasize the need for multicenter registry studies and prospective trials to refine treatment strategies. As advances in genomic medicine and immunotherapy evolve, guideline updates will be essential to ensure optimal patient care.