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.

Malignant nerve sheath tumors comprise approximately 5% of all soft tissue sarcomas; only 8% to 15% of these tumors arise in the head and neck. Most tumors appear as a rapidly expanding nonpainful mass in the face or lateral neck. Reported association with Von Recklinghausen's disease varies from 26% to 70%. Wide surgical excision is generally the recommended primary treatment. Recently, there has been a trend to include postoperative radiation therapy as a primary modality.

Five cases of a previously undescribed variant of epithelioid sarcoma are presented. This variant differs from the usual lesion in its absence of the typical necrobiotic nodular epithelioid pattern. It is instead composed of deceptively bland fibrohistiocytic and myoid cells arranged in a fibroma‐like or dermatofibroma‐like pattern with an affinity for osseous involvement. The clinical presentation, ultrastructural features, and presence of vimentin and low molecular weight keratin within the tumor cells justifies their designation as an epithelioid sarcoma variant. Cancer 1992; 69:1382‐1395.

The seventh case of primary malignant mesenchymoma of bone is reported. It is compared to the other six cases in the literature and clinicopathologic pattern of this entity is developed. Primary malignant mesenchymoma of bone is compared to mesenchymal chondrosarcoma and dedifferentiated chondrosarcoma. Differences as well as similarities are discussed and a more current classification scheme for malignant mesenchymoma of bone is proposed.

Abstract‘Benign metastasizing mixed tumours’ are enigmatic lesions of the parotid gland. The authors, through the illustrations of a case and review of the literature, conclude that the tumours are unrecognized and currently unclassified malignancies.