BMC Cancer 2003, 3 http://www.biomedcentral.com/1471-2407/3/17 times seems arbitrarily chosen, perhaps based on praxis rather than updated analyses. When different size thresh- olds have been tested to distinguish patients with poor and good prognosis, 6 cm [9], 8 cm [10] and 10 cm [4] have been used. Probably each increase of size increases the risk for metastatic spread. Trovik et al [11] found that the relative risk for metastatic disease increased by 1.5 per 5 cm increment of tumor size. Suit et al [12] studied 6 groups of size and found an increasing risk of metastases with increasing size. We made the same observation. We also found that when size is dichotomized at 5 cm, the mean size of small tumors (1–5 cm) is the same irrespec- tive of whether the tumor is superficial or deep. However, in the large tumor group (>5 cm) the size of deep tumors were one third greater than that of superficial tumors. This seems to explain the prognostic value of depth when size is dichotomized at 5 cm. This prognostic effect of tumor depth was evident only in large and high-grade tumors where the deep-seated tumors had the poorest prognosis (Figure). Although we observed the effect only in large and high-grade tumors this subset comprises about one half of all tumors (Tables 4,5,6,7). The reason that we could not find any prognostic importance of tumor depth in large but low-grade tumors is probably the good prog- nosis for low-grade tumors. Since we found tumor depth of no major prognostic value we assessed prognostication based on only grade and size, but with size divided into 3 groups (<5, 6–10, >10 cm) and found that patients could be allocated to 4 groups, 1 with low grade tumors (either grades I-II or grades I-III) with good survival irrespective of tumor size and 3 groups of patients with high grade tumors and with increasing size being associated with decreasing survival. This find- ing is by no means new; see for example Ramanathan et al [8] and references therein. We also found this staging prognostically more discriminative than a system based on the number of dichotomized risk factors – e.g. grade, size and depth – present. For example, a tumor with two risk factors is either a deep and large, a deep and high- grade, or a large and high-grade tumor. In our patient series the survival rates varied considerably between these combinations, being highest for deep and large tumors and lowest for for high-grade and large tumors (Tables 4,5,6,7) In conclusion, we found no evidence of tumor depth being a major prognostic factor for metastatic disease in soft tissue sarcoma of the extremity and trunk wall. Only when tumor size is dichotomized at 5 cm does depth contribute prognostic information. We suggest it is con- ceptually better to disregard depth and optimize the infor- mation from size by using more than two size categories. 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