It is known that hypertrophy of adipose tissue, fibrosis in the skin and subcutaneous tissue, and degeneration of the lymphatic vessels are present in lymphedema.1-5 After lymphadenectomy or radiotherapy, lymphatic flow is dammed up and accumulation of lymphatic fluid in the distal lymphatic vessels occurs.6 In turn, this causes an increase in lymphatic inner pressure.7 However, it is still unknown how injury of the lymphatic vessels progresses.