Results: mRNA and protein of E-cadherin were not expressed in S3KO cells. IL-6 up-regulated E-cadherin in control cells but not in S3KO cells, and induction of constitutively active mutant of STAT3 restored E-cadherin level in S3KO cells. Interestingly, membrane-bound beta-catenin expression was not affected, but released to cytosol in S3KO cells. S3-KO cells showed almost normal proliferation but did not form cell cluster due to lack of E-cadherin. Electron-micrograph confirmed lack of intercellular adhesion structures (desmosome) in S3KO cells. Also in L-S3KO mice, hepatocytes lack desmosome structure and cell adhesion. Objective: ALK positive anaplastic large cell lymphoma (ALCL) is characterized by anaplastic lymphoma kinase (ALK) expression, most commonly associated with the t (2;5)(p23;q35), fusing the ALK and nucleophosmin (NPM) genes. However, in a significant proportion of cases the ALK gene has a number of other than NPM translocation partners. The aim of the study was to detect the NPM/ ALK fusion gene and the other possible fusion genes. Method: NPM/ALK was detected by RT-PCR, NPM/ ALK negative lymphomas were analyzed by ALK specific Rapid Amplification of 5´cDNA Ends (5´RACE). We prepared Q-RT-PCR assay for quantification of 3Á LK mRNA. Molecular findings were correlated with I-FISH. Results: We analysed 42 ALK positive ALCL. Chromosomal breakpoints affecting the ALK locus were detected by I-FISH in all patients. The NPM/ALK was detected in 32/42 patients. 5´RACE identified ATIC/ALK in 3, CLTC/ALK in 2 patients. Other fusion genes (TPM4/ALK, TPM3/ALK, ALO17/ALK) were found in one patient. In all specimens, overexpression of 3´ALK mRNA suitable for the minimal residual disease (MRD) detection was found. Objective: A 17 year-old girl, presented with an osteolytic epiphyseal lesion of the distal ulna. Based on histopathological examinations, the lesion was classified as giant cell tumor of bone (GCT). Four years later, the girl developed a second lesion at the same site. The histopathological examination revealed aneurysmal bone cyst (ABC) with solid spindle celled and giant celled areas which raised a question of a recurrent GCT or a primary ABC. The aim of this study was to analyze the clonality of these two processes. Determination of maternal and paternal X chromosome activation status is useful in the diagnostic analysis of nonrandom X inactivation patterns. Method: The human androgen receptor (HUMARA) gene polymorphism assay was used to identify the clonality of these two processes. Results: The patient was identified as heterozygous for the HUMARA allele. The GCT and ABC samples exhibited a monoclonal pattern, but one of them was with maternal and the other with paternal X chromosome origin. Conclusion: The findings of this case report demonstrate the clonal behavior of both lesions with different clonal patterns. The above investigation proved to be helpful in distinguishing between recurrent GCT and de novo ABC in the field of previous surgical intervention. . In all specimens gen Her2/neu was quantifed agains reference gen by qRT-PCR method (LyghtCycler® 480 II, Roche). Results: The results of cytogenetic analysis have been showed in 40 % that didn´t corespond with the results of qRT-PCR quantification. On the contrary the results of IHC was correlated with the results of qRT-PCR in 100 %. Methods SISH vs FISH has in 25 % different of results. In regard to the quality of ISH signals the SISH is more preferable for determination Her2/neu. Conclusion: A pilot study conducted on a group of 20 patients showed that among the methods used in the process of determining HER2/neu amplification are significant differences, even in evaluation and interpretation of test results. Regardless of the histological type of tumors (diffuse and intestinal type) as problematic for the evaluation of samples proved to be endoscopic route.