Abstract: This paper reports a case of rare secondary lymphedema with pretibial myxedema, which was diagnosed as secondary lymphedema of both lower extremities by completing a comprehensive examination of the lymphatic system. After partial resection and biopsy were performed on the tumor of the left lower leg, it was initially diagnosed as a fibromyxoid tumor (intermediate type), more likely superficial CD34-positive fibroblastic tumor with myxodegeneration. As the tumor of the left lower leg was rare, after consulting the opinions of some domestic hospitals, and combined with the medical history and hormone treatment effect, our final diagnosis was left anterior tibial myxedema. After more than 10 months of external treatment with halometasone ointment, all nodules became flat, leaving light brown pigmentation spots. This article discusses the differential diagnosis of this disease, with the aim to enhance clinical doctors' understanding of the disease.