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Case Reports in Medicine
Volume 2010, Article ID 327591, 5 pages
http://dx.doi.org/10.1155/2010/327591
Case Report

Well-Differentiated Extraskeletal Osteosarcoma Arising from the Retroperitoneum That Recurred as Anaplastic Spindle Cell Sarcoma

1Department of Pulmonary Medicine (Surgery), Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama, 232-0024, Japan
2Department of Surgery, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan
3Department of Pathology, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan
4Department of Pathology and Laboratory Medicine, Kohnodai Hospital, National Medical Center of Japan, 1-7-1 Kohnodai, Ichikawa, Chiba, 272-8516, Japan
5Department of Urology, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan

Received 10 November 2009; Accepted 6 January 2010

Academic Editor: Michael H√ľnerbein

Copyright © 2010 Hiromasa Arai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Extraskeletal osteosarcoma is an uncommon high-grade malignant soft tissue sarcoma. Well-differentiated extraskeletal osteosarcoma is thought to have a better prognosis than classical extraskeletal osteosarcoma, but dedifferentiation after recurrence has also been reported. We present a case of a primary retroperitoneal extraskeletal osteosarcoma in a 62-year-old Japanese woman. Abdominal CT revealed a large mass with diffuse calcification in the right retroperitoneal space and tumor resection was performed. The histopathological diagnosis was well-differentiated retroperitoneal extraskeletal osteosarcoma. She was followed up by CT every 6 months without adjuvant radiotherapy and chemotherapy for 31 months until anaplastic high-grade spindle cell sarcoma recurred in the retroperitoneum. Our case is the seventh reported description of well-differentiated extraskeletal sarcoma, and the first to arise in the retroperitoneum and recur as an entirely dedifferentiated spindle cell sarcoma.