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

Table 1

Summary of reported cases with well-differentiated extraskeletal osteosarcomas.

Case	Year	First author	Age	Sex	Site	Size (cm)	Treatment	Follow-up and outcome
1	1953^a	Umiker	44	M	Rt. thigh	5	resection	Died with widespread metastasis after 5 years
2	1989	Present	57	F	Lt. knee	24	resection	Alive 5 years after surgery
3	1991	Yi	74	F	Lt. axilla	15	resection	Alive 2 years after surgery
4	2003	Okada	35	F	Lt. leg	11	resection	Alive 4 years after surgery
5	2005	Abramovici	40	F	Lt. upper back	9×6×5	resection	Alive 2 months after surgery lost in follow-up
6	2005^a	Abramovici	32	M	Bil. thighs, buttocks and lt. paravertebral area (max. lesion)	16×7×8	resection and chemo	Alive with widespread metastasis 4 years after initial surgery
7	Present case^a		62	F	Retroperitoneum	14×11×8	resection	Died with widespread metastasis after 33 months

chemo: chemotherapy 
a: recurred as a high-grade malignancy