Well-differentiated extraskeletal osteosarcoma arising from the retroperitoneum that recurred as anaplastic spindle cell sarcoma.
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.
Arai
Hiromasa
H
Department of Pulmonary Medicine (Surgery), Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama, 232-0024, Japan.
Rino
Yasushi
Y
Nishii
Teppei
T
Yukawa
Norio
N
Wada
Nobuyuki
N
Oshiro
Hisashi
H
Ishida
Tsuyoshi
T
Nakaigawa
Noboru
N
Masuda
Munetaka
M