Results: The modified methacarn fixation provided a histomorphological quality comparable to the formalin-fixed tissue specimens. The immunoreactivity was superior in the buffered than in the untreated formalin and the preservation of protein antigenicity in normal and pathologically changed tissues tested with several antibodies was excellent with the use of alcohols with acetic acid. The acidic ethanol and the modified methacarn fixative showed the best preservation of the integrity of RNA in satisfactory quantity and quality of fragments up to 577 bp, which was reliable for relative evaluation of gene expression. Objective: cFLIP prevents the apoptosis by caspase 8 inhibition, its overexpression correlates with the progression of different tumors. Thymomas and thymic carcinomas are thymic epithelial tumors, in which the regulation of apoptosis is still unknown. We investigated the role of cFLIP in regulating the viability of thymus carcinoma cell line 1889c using an RNA Interference. The cell line HaCat was used as a control. Method: 1889c and HaCat cell lines were transfected with an established "short Hairpin" pIRES/PURO cFLIP-shRNA expression vector. CFLIP suppression and its Effect on pro and antiapoptotic molecules were analyzed using q-PCR and western blot. Apoptosis was quantified using the flow cytometry.