Evaluation of putative molecular biomarkers in abdominal and retroperitoneal leiomyosarcomas

Leiomyosarcomas (LMS) are diverse tumours with different biological behaviour. To evaluate the biological nature of intraabdominal and retroperitoneal leiomyosarcomas we retrospectively examined the immunoreactivity of p53, bcl-2 and proliferative activity expressed as Ki-67-labelling index in 43 tumours.

Immunohistochemical staining was performed using a peroxidase-streptavidin method on paraffin-embedded sections using specific anti- p53, anti- bcl-2 and anti Ki-67 monoclonal antibodies.

Of 43 tumours, seven were located in the stomach, 11 in the small or large bowel, 12 in the uterus, 11 in the retroperitoneum and two cases in the urinary bladder. Five-year disease-free survival was 46.5%. Twenty-three patients (53.4%) died of the disease. Positive immunoreactivity for p53 and bcl-2 was found in 18 (41.9%) and 26 patients (60.5%), respectively. Positive Ki-67 staining was observed in eight patients (18.6%). Proliferative indices were higher in LMS with high mitotic activity (P=0.004) and high grade (P=0.009). All Ki-67 positive LMS were intermediate or high-grade tumours. Ki-67-labelling index showed inverse relationship to bcl-2 expression. A trend towards higher survival and expression of bcl-2, p53 or Ki-67 was found.

Our results demonstrate that p53 and bcl-2 are expressed in a substantial number of intraabdominal and retroperitoneal leiomyosarcomas. In our study, the expression of these biomarkers did not predict patient outcome. Higher Ki-67 labelling indices were found in more biologically aggressive leiomyosarcomas.