PURPOSE: Angiosarcoma is a rare tumor, representing 1% of all soft tissue sarcomas, with an annual incidence of 2-3 cases per 1,000,000 population. Its mediastinal location correspond to only to 0.02%. Different mutations or methylation of the promoter RB suppressor gene have been implicated in the etiology of sarcomas. However in mediastinal angiosarcoma RB gene has not been completely explored.
METHODS: In tumoral tissue of angiosarcomas RB expression was detected by immunohistochemistry (RB polyclonal antibody, C-15 AA 928, Santa Cruz Biotechnology, Santa Cruz, CA). 2 Tumor tissue DNA was treated with a bisulphite genomic-sequencing method. Indirect immunoperoxidase with CD 31, CD 34, AIUE (Anti Ulex europeas ) and FVIII markers were employed to confirm vascular structures of the tumors.
RESULTS: RB expression was detected in > 90% of cell's nuclei of well limited tumor and in 25-30% of cell's cytoplasm of invasive primary mediastinal angiosarcoma A heterogeneous pattern of methylation in CpG sites of promoter region of the RB gene was found. All immunoperoxidase markers were positive for limited and invasive tumors except FVIII that was positive only in limited.
CONCLUSION: Mediastinal angiosarcomas are rare tumors with high degree of malignant activity. A methylated heterogenous pattern may be associated with a low percentage (30%) of protein RB marked cells in invasive tumors, suggesting that the defficiency of protein RB ocurrs in more advanced stages when the neoplasia become invasive and is different than in well limited tumors with higher quantity of protein RB (90%). Low protein RB may be associated with the invasive malignant characteristics of mediastinal angiosarcomas.
CLINICAL IMPLICATIONS: Molecular analysis of mediastinal angiosarcomas is important to evaluate their malignat activity.DISCLOSURES: The authors have nothing to disclose.
DISCLOSURE: Raul Cicero, No Financial Disclosure Information; No Product/Research Disclosure Information