BMC Cancer 2009, 9:205 Table 1: Patient characteristics Variables Age, Median (range) Gender Male Female Presentation status Biopsy No prior biopsy or treatment Prior excision Histologic variant Well differentiated Myxoid Dedifferentiated Round Pleomorphic Primary site Retroperitoneum Without contiguous organ resection With contiguous organ resection Lower extremity Upper extremity Trunk Tumor burden Median (cm, range) Margins Negative margins Positive micro margins Positive gross margins Postoperative radiotherapy for primary disease Median dose (cGy) Negative/microscopic/gross positive (%) Yes No cm (range, 2–48). The distribution of histologic subtypes were as follows: well differentiated in 50 patients (53.2%), myxoid in 22 patients (23.4%), dedifferentiated 15 patients (16.0%), round cell 5 patients (5.3%), and pleomorphic in 2 patients (2.1%). We classified the histo- logic grade into two categories according to previous study [13]. There were 72 patients with low grade (well- differentiated and myxoid tumors) and 22 patients with high grade tumors (dedifferentiated, round cell, pleomor- phic tumors). Fifty patients had negative resection mar- gins, 32 had microscopically positive margins, and 12 had grossly positive margins. Nearly half of the tumors were located in the retroperitoneum; one third of these patients required resection of contiguous organ other than kidney. We also analyzed clinical characteristics according to the histologic grade (low vs high) as shown in Table 1. Survival analyses After a median follow-up duration of 48 months (range, 4.5–166.4 months), 72 (76.6%) patients remained alive 56 (20–80) 53 (56.4%) 41 (43.6%) 49 (52.1%) 20 (21.3%) 25 (26.6%) 50 (53.2%) 22 (23.4%) 15 (16.0%) 5 (5.3%) 2 (2.1%) 44 (46.8%) 32 (34.0%) 12 (12.8%) 24 (25.5%) 9 (9.6%) 17 (18.1%) 14 (2–48) 50 (53.2%) 32 (34.0%) 12 (12.8%) 5300 (2500–6000) 31 (33.0%) 17/10/4 (54.8/32.3/12.9) 63 (67.0%) 55 (20–80) 42 (58.3%) 30 (41.7%) 38 (52.8%) 17 (23.6%) 17 (23.6%) - - - - - 31(43.0%) 23 (31.9%) 8 (11.1%) 23 (31.9%) 9 (12.5%) 9 (12.5%) 13 (2–45) 42 (58.3%) 24 (33.3%) 6 (8.3%) 5400 (2500–6000) 22 (30.5%) 13/8/1 (59.1/36.4/4.5) 50 (69.4%) High (n = 22) 58.5 (24–75) 11(50.0%) 11(50.0%) 11(50.0%) 3(13.6%) 8(36.4%) - - - - - 13 (59.1%) 9 (40.9%) 4 (18.2%) 1(4.5%) 0 (0) 8 (36.4%) 15 (2–48) 8 (36.4%) 8 (36.4%) 6 (27.3%) 5000 (2600–6000) 9 (40.9%) 4/2/3 (44.4/22.2/33.3) 13 (59.1%) http://www.biomedcentral.com/1471-2407/9/205 Total (n = 94) (%) No. of patients Low (n = 72) and 22 (23.4%) patients died of the disease. The 5- and 10-year overall survival probabilities were 78.1% and 67.5%, respectively (Figure 1). OS according to histologic subtype is shown in Table 2. OS was significantly different according to the histologic subtype (P < 0.001). Histologic subtypes were dichot- omized into two groups (well-differentiated and myxoid tumors vs others). The 5-year OS rates for low and high grade tumors were 86.1%, and 48.6%, respectively. While patients with microscopically negative and positive mar- gins had 5-year OS of 88.1% and 75.0%, respectively, patients with grossly positive margins had a significantly decreased 5-year OS of 44.0%. For the tumor burden, patients with tumor diameter less than 10 cm had signifi- cantly prolonged OS compared to those with greater than 10 cm (P = 0.013). The 5-year OS rates were 100% and 67.3% for patients with tumor diameter less and greater than 10 cm, respectively. For the primary sites, extremity site showed the most favorable prognosis (upper extrem- Page 3 of 8 (page number not for citation purposes)