Evaluation of dystrophin expression by immunohistochemistry as a prognostic factor in leiomyosarcomas (LMS).

Abstract

e23525 Background: Leiomyosarcomas (LMS) are soft tissue sarcomas that derive from smooth muscle cells and can arise anywhere in the body (most frequently in extremities, uterus or retroperitoneum). The clinical prognostic factors are well established but molecular factors influencing prognostic are unknown. The DMD gene, which codifies for the dystrophin protein, has been proposed as tumour suppressor gene in LMS. The aim of our study is to evaluate dystrophin expression in LMS and its relation with the patient prognosis. Methods: A total of 103 patients (pts) with LMS were analysed. Clinical and pathological data were collected retrospectively from patients’ electronic board system. Dystrophin expression was analysed by immunohistochemistry (IHC) in paraffin embedded tissue LMS samples using the Novocastra NCL-DYS2 (Leica Biosystems). Semiquantitative assessment of the staining was classified from score 0 to 3 (0 = no dystrophin expression, 1 = low expression, 2 = moderate expression, 3 = high expression). Results: Of all 103 pts, 70 (68%) had localized disease and the majority of tumours were larger than 5 cm (75%). The most frequent locations of primary LMS were extremities (n = 31; 30.1%), uterus (n = 23; 23.2%) and retroperitoneum (n = 21; 20.4%). Most LMS were high grade (G): 7 pts G1 (6.8%), 35 pts G2 (34%) 2 and 53 pts G3 (51.5%). 50 of all grade LMS (48.6%) had loss of dystrophin expression (score 0), 17 (16.5%) had score 1, 23 (22.3%) score 2 and 10 (9.7%) score 3. Loss/low dystrophin expression measured as score 0 or 1, was more frequent in grade 3 LMS compared to grade 2 or grade 1 (77.4% vs. 57.1% vs. 16.7%; p = 0.005). There were no differences in dystrophin loss between localized or metastatic disease at diagnosis (64.2% vs. 72.2%; p > 0.05). In our series, loss or reduced dystrophin expression did not correlate with the risk of relapse in localized patients or overall survival in metastatic patients. Conclusions: Loss of dystrophin expression is a common event in LMS. Loss/low dystrophin expression is more frequent in grade 3 LMS compared to grade 2 and grade 1 LMS. Loss of dystrophin expression did not correlate with risk of relapse or overall survival in our series. Additional genetic evaluations to study DMD in LMS are underway.