In our current study, we have documented the prognostic significance of the tumour grade determined by a MIB-1 score based grading system in patients with myxoid liposarcoma. Univariate analysis revealed that the tumour site, RC component content, necrosis, mitosis, MIB-1 LI, and tumour grade had a significant impact on overall survival, in accordance with previous studies.13–15
Multivariate analysis showed that, of these variables, the tumour grade determined by the grading system was the most important adverse prognostic factor.
The prognostic importance of the RC component has been acknowledged in previous studies. Patients (n = 5) with > 5% RC components in their initial tumours had a significantly higher incidence of metastasis or death from disease than those (n = 7) with < 5% RC components, despite the small sample size.13
In a study of 24 patients, > 25% RC components was significantly associated with adverse survival.14
Our patients with < 25% RC components had significantly better five year and 10 year survival rates than did those with > 25% RC components. A significant difference was also found when the cutoff value of RC components was set at 75%, which was in accordance with the results of previous studies.14,15
However, the correlation between the proportion of RC components and the clinical outcome may depend on the difficulty in measuring the RC components or transitional areas. There was no significant difference between the risk of an adverse outcome in patients with myxoid and transitional areas without RC components and those with myxoid areas alone.14
“The tumour site, round cell component content, necrosis, mitosis, MIB-1 labelling index, and tumour grade had a significant impact on overall survival”
It has been reported that the degree of necrosis correlates with the clinical outcome.16–18
Spontaneous tumour necrosis identified in four of 95 patients with myxoid liposarcoma correlated with an increased risk of metastases and death.13
In our study, the presence of necrosis in 14 patients was also associated with, and was a significant predictor of, poor outcome. Fewer workers have analysed p53 immunoreactivity and examined the relation between p53 overexpression and clinical outcome.19,20
In the study by Antonescu et al
, 12 of 71 myxoid liposarcomas examined overexpressed p53, which was associated with an adverse prognosis on multivariate analysis (RR = 3.2; p < 0.05).15
In our present study, three of five patients whose tumours overexpressed p53 had died by the time of the final follow up. However, no significant association was found between p53 status and survival (p = 0.20). Overexpression of p53 in myxoid liposarcomas seems to be uncommon, and further studies are needed to confirm this. Liposarcomas are often large and a large tumour size is associated with a poor prognosis.21,22
In a previous study, the size of myxoid liposarcomas did not have a significant effect on overall survival.13
Nevertheless, several variables were analysed along with tumour size in our study, the results of which may support this concept. Metastases occurred in 14 patients; however, there was no significant correlation between metastasis and tumour grade.
Take home messages
- Multivariate analysis showed that the tumour grade determined by the MIB-1 score based grading system (MIB-1 system) is the most important adverse prognostic factor in patients with myxoid liposarcoma
- This grading system is based on three variables: tumour differentiation/histological type, necrosis, and the MIB-1 (Ki-67) score
In conclusion, multivariate analysis of our results suggests that the tumour grade determined by the MIB-1 score based grading system (MIB-1 system) is the most important adverse prognostic factor in patients with myxoid liposarcoma.