[Expression of CD133 in primary retroperitoneal leiomyosarcoma and its relationship with Ki-67]

To explore the correlation between CD133 and proliferative marker Ki-67 in primary retroperitoneal leiomyosarcoma and evaluate their prognostic values.

A total of 50 primary retroperitoneal leiomyosarcoma samples were collected at our hospital from January 2000 to December 2012. There were 9 males and 41 females. All samples were analyzed for CD133 and Ki-67 protein expression by PV6000 immunohistochemistry. Their median age was 49 (27-75) years. All cases were successfully followed up.

CD133 expression was detected in 74.00% (37/50) of primary retroperitoneal leiomyosarcoma samples. The CD133-positive rates of histological grades I & II primary leiomyosarcoma were 7/13 and 76.70% (23/30) respectively. All grade III samples (n = 7) were CD133 positive. And the expression of CD133 had a positive correlation with tumor size, mitotic counts and histological grade (χ(2) = 4.925, 4.525, 10.080; P = 0.026, 0.033, 0.013). The survival time of CD133-positive patients with M (Q1, Q3) was 32 (17, 56) months versus 44 (26, 65) months for those negative ones. The expression of Ki-67 was detected in 84.00% (42/50) of primary retroperitoneal leiomyosarcoma samples and its expression showed a positive correlation with mitotic counts. The expressions of CD133 and Ki-67 were positively correlated in primary retroperitoneal leiomyosarcomas (P = 0.009). Log-rank test showed that positive expressions of CD133 and Ki-67 and 5-year patient survival rate were correlated (P = 0.021, 0.049). Multivariate analysis showed that CD133 and mitotic counts were independent prognostic indicators for primary retroperitoneal leiomyosarcomas (HR = 2.040, 2.422; P = 0.000, 0.018).

CD133 plays an important role in the progression of primary retroperitoneal leiomyosarcomas so that it may be used as a marker for patient prognosis. Combined detection of CD133 and Ki-67 has a prognostic value in patients with primary retroperitoneal leiomyosarcoma.