Soft Tissue Sarcoma Patterns multiplicity, heterogeneity and growth characteristics

Soft tissue sarcomas (STS) represent a group of rare and heterogenous tumors that optimally should be diagnosed and treated within multidisciplinary teams. This thesis has studied various aspects ? pathological, genetical, and clinical ? of STS. In study I, we demonstrated that 20% of the patients in a population-based series of 818 STS developed second primary malignancies. An increased risk of developing a second malignancy was identified (SMR 1.3; 95% CI=1.0-1.5), with a particularly high risk of developing a second STS (SMR 17.6; 95% CI=8.1-33.5). Study II included 13 patients who had developed at least two primary STS and we applied array-based comparative genomic hybridization to study the genetic profiles of these tumors. Cluster anaysis and comparison between the genetic profiles suggested that 8 cases represented second primary STS, whereas 5 cases likely represented soft tissue metastases. In study III cDNA microarray was applied to 26 synovial sarcomas and identified differentially expressed genes in relation to gene fusion type. Among the discriminators were several genes that have previously been found to be up-regulated in SS, including AXL, ZIC2, SPAG7, AGRN, FOXC1, NCAM1. In study IV we assessed the impact of targeting peripheral versus central tumor areas using tissue microarray-based staining for Ki-67 in leiomyosarcomas and demonstrated that the Ki-67 expression was higher in the tumor periphery in 18/25 tumors. These observations suggest that Ki-67 evaluation for prognostic purposes should be standardized regarding the part of the tumor investigated. In study V, peripheral tumor growth pattern was evaluated on preoperative MRI with correlations to microscopical growth pattern and prognosis. All tumors with diffuse infiltration on MRI also showed microscopical infiltration, whereas MRI failed to identify infiltration in one-third of the microscopically infiltrative tumors. Diffusely infiltrative growth on MRI correlated with prognosis with a 2.5 times increased risk of metastases (p=0.01) and a 3.7 times higher risk of local recurrence (p=0.02). In summary, we have demonstrated that patients with STS are at increased risk of developing second primary tumors, including STS, with genetic profiles supporting independent tumor origin. We have also demonstrated that the underlying gene fusion type in synovial sarcoma influence the gene expression profile. Finally, the tumor periphery seems to provide the best information; our studies suggest that evaluation of Ki-67 staining should be standardized, perhaps to the periphery, and that MRI-based classification of the peripheral tumor growth pattern may provide prognostic informatio