Benign giant cell tumor of bone with osteosarcomatous transformation (”dedifferentiated" primary malignant GCT): report of two cases

Abstract

It is not uncommon for sarcomatous transformation of giant cell tumor (GCT) of bone to occur after radiation, but rarely does malignant transformation occur spontaneously, with less than 15 cases reported up to 1995. Only four of these cases have been documented in detail. We report two additional cases of GCT of bone spontaneously transforming or "dedifferentiating" into osteosarcoma without radiation therapy. The first case is absolutely unique and most interesting in that the dedifferentiation process occurred in one of multiple GCT lung metastases 6 years after successful eradication of a primary tibial tumor. The right lung was resected due to development of a large tumor, and at pathologic examination, demonstrated several small nodules of conventional GCT and a much larger, 14-cm mass composed of a mixture of GCT and high-grade osteosarcoma. The second case involved a physician, who had a large tumor in the sacrum with vague symptoms for 8 years. Open biopsy revealed conventional, benign GCT of bone with a secondary aneurysmal bone cyst. Complete curettage 2 weeks later revealed, in addition to areas of conventional, benign GCT a second component of very high grade osteosarcoma. Both patients died less than 1.5 years from diagnosis. This report of osteosarcomatous transformation of a conventional GCT of bone strengthens the theory that there is a mesenchymal cell line in GCT that may spontaneously transform to sarcoma.

The prognostic factors of recurrent GCT: a cooperative study by the Eastern Asian Musculoskeletal Oncology Group

“…27 Bertoni F et al 28 reported 6 cases of post surgical secondary malignant GCT without prior irradiation. They also mentioned that the average interval between benign GCT and sarcoma diagnosis of these patients was 18 years, much longer than the average interval observed in patients who received previous radiotherapy (9 years).…”

Fine-needle aspiration biopsy of skeletal versus extraskeletal osteosarcoma

“…11 Recent evidence suggests that spontaneous malignancy in giant cell tumors most certainly represents a form of dedifferentiation. 12,13 When malignant transformation of a benign giant cell tumor occurs, it usually presents as a fibrosarcoma or OS. 11 One of our cases initially was diagnosed by FNAB as a giant cell tumor.…”

Histogenetic Characterization of Giant Cell Tumor of Bone

“…After intralesional or even marginal excision, it locally recurs in 20% to 40% of cases [39], and in less than 5% of cases, GCT may develop histologically benign metastases [3]. GCT may also spontaneously undergo sarcomatous transformation [5], the risk of progression being greatly increased by radiation [6]. The outcome of this lesion cannot be predicted on the basis of histologic or radiographic criteria [9,23], and in the absence of a clear histogenetic origin, GCT is currently classified among lesions with an uncertain derivation and named after its peculiar morphologic appearance.…”