Transformation of Benign Giant Cell Tumor of Bone Into Epithelioid Angiosarcoma
In this article, we report a case of transformation of a benign giant cell tumor (GCT) of the calcaneus into an epithelioid angiosarcoma. The patient presented to our service in 2003 and was followed until 2014. Transformation occurred 11 years after curettage, cryotherapy, cementation, and a well-documented disease-free interval. Longitudinal radiographs, magnetic resonance imaging, and histopathology were evaluated by the same medical team.
There are only a few case reports and case series of malignancy associated with GCT of bone. To our knowledge, this case report is the first to describe an assessment of the transformation of a benign GCT of bone into an epithelioid angiosarcoma. Orthopedic surgeons, radiologists, oncologists, and pathologists should be aware of the potential for transformation of benign GCTs to high-grade sarcomas after a long disease-free interval.
Discussion
Malignant transformation of a benign GCT is extremely rare, especially in cases in which the tumor bed has not previously undergone radiation therapy. Although the literature includes historical case reports, primary and secondary malignant GCTs comprise <9% of all GCTs.11,13,14 Primary bone epithelioid angiosarcoma is also extremely rare, especially in the calcaneus; only 1 case is described in the literature.15 In this article, we report on a benign GCT of bone that transformed into an epithelioid angiosarcoma more than a decade after the GCT was treated with curettage and cementation.
The fact that the malignant areas of a previous tumor may have been missed because of sampling error is important for benign GCT of bone in the early postoperative period, as distinguishing between early malignant transformation and an overlooked malignancy may not be possible. However, transformation is more likely the case when a benign GCT becomes a high-grade malignancy after a long disease-free interval. Several authors have indicated that a benign GCT tumor recurring with a secondary malignancy 2 to 5 years after initial GCT treatment suggests malignant transformation.16 Grote and colleagues10 compiled reports of malignant transformation of GCT of bone and described the clinicopathologic features of secondary malignant transformation of GCTs. The data they compiled and data from several other studies indicate a poor prognosis after malignant transformation of GCT; 4 years after diagnosis, mean survival is 40% to 50%.10,16 The most common clinical presentation of transformation of GCT into malignancy is pain, often with coincident swelling of the native wound bed. However, a few cases have been identified with radiologic imaging alone and without a period of clinical symptoms.16
To our knowledge, this case report is the first to describe a longitudinal assessment of the transformation of a benign GCT of bone into an epithelioid angiosarcoma. Whereas an earlier reported GCT of bone transformed into epithelioid angiosarcoma after irradiation,12 our patient’s GCT of bone transformed without irradiation. GCTs of bone are locally aggressive benign tumors and are relatively rare. Malignant transformation of a benign bone tumor a decade after initial, definitive treatment is concerning, especially given the poor prognosis after malignant transformation in this clinical scenario. Current adjuvant treatments have not changed the prognosis. The literature includes a wide variety of histologic transformations, including high-grade sarcomas, after a long disease-free interval. Although malignant transformation of benign GCTs is rare, clinicians should be aware of the potential. Interval monitoring of GCTs may be necessary in patients with symptoms concerning for malignant transformation—pain or swelling in the wound bed—and patients should know to immediately inform their physician of any changes in pain level or local wound bed. Clinicians should maintain a high clinical suspicion for malignant transformation or late recurrence of GCT in a patient with new pain at the site of a previously treated GCT of bone with a disease-free interval of several years.
