Venous malformations (VMs) are the most common type of vascular malformation and often cause pain, swelling, coagulopathy, and severe impairment of quality of life. Conventional treatments, including partial resection or sclerotherapy, may be insufficient for extensive lesions with skin involvement owing to bleeding risks and limited efficacy. We report the case of a 57-year-old man with an extensive thoracoabdominal VM involving the skin, subcutaneous tissue, and muscles. A two-stage surgical approach with serial excision and bilateral free anterolateral thigh (ALT) flap reconstruction was performed. The first surgery removed the dorsal lesion (26×25 cm) , followed by reconstruction using a right ALT flap. The second surgery was performed 11 months later, and the ventral lesion (20×15 cm) was resected, followed by reconstruction with a left ALT flap. Both flaps survived without major complications. Postoperatively, pain resolved, cosmesis improved, and the patient resumed normal activities. ALT flaps provide sufficient tissue volume and long pedicles for safe anastomosis away from diseased areas and allow reconstruction without repositioning. This case demonstrates that staged excision followed by free ALT flap transfer can achieve effective functional and aesthetic outcomes for giant VMs with skin invasion while minimizing complications.
