Gorham-Stout disease causes gradual bone loss (osteolysis) due to an abnormal overgrowth of lymphatic vessels. This rare disease is usually seen in younger people. The etiopathology of Gorham-Stout disease remains unclear. The disease is pathologically characterized by the proliferation of the vascular or lymphatic vessels and, finally, bone matrix destruction. These pathological changes lead to the presence of massive osteolysis on plain radiographs. Thus, plain radiograph findings may lead physicians to consider tumoral conditions, especially metastasis. There are several other conditions on the differential diagnosis list of massive osteolysis, such as metabolic, infectious, malignant, and immunological conditions. After excluding all possible disorders, the disease can be considered in the differential diagnosis. The treatment of the disease is symptom-based, but there is no consensus. Pharmacological methods should be considered first-line treatment. If there is no regression in the course of the disease despite pharmacological treatment, radiotherapy and resection arthroplasty are the treatment of choice in the later stages. In this case report, we present a case of Gorham-Stout disease, which was treated by pharmacological methods. During the one and half year follow-up, the local control of the disease was achieved without any surgical intervention.