A rational approach to the CNS tumors diagnostics.

The new WHO classification of CNS tumors is largely based on molecular diagnostic. Without molecular methods some entities can no longer be diagnosed. We are trying to show a rational approach to the CNS tumors diagnostics, which is based on conventional molecular methods such as RT-PCR, Sanger sequencing, MLPA, extended by the next generation sequencing (NGS) and methylation SNP array.

Gastrointestinal stromal tumors - Summary of mutational status of the primary/secondary KIT/PDGFRA mutations, BRAF mutations and SDH defects.

The most important findings revealing pathogenesis, molecular characteristics, genotyping and targeted therapy of gastrointestinal stromal tumors (GISTs) are activated oncogenic mutations in KIT and PDGFRA genes. Imatinib mesylate (IM), which inhibits both KIT and PDGFRA receptors, significantly improved treatment of advanced (metastatic, recurrent, and/or inoperable) GISTs. However, in a significant number of patients the treatment fails due to the primary or secondary resistance to targeted therapy. Most common cause of secondary resistance is a presence of secondary mutations. Approximately 15% of adult patients with GISTs are negative for mutations in KIT or PDGFRA genes. These so-called wild-type GISTs appear to be characterized by other oncogenetic drivers, including mutations in BRAF, RAS, NF1 genes, and subunits of succinate dehydrogenase (SDH) complex. In the present study we investigated 261 tumour specimens from 239 patients with GIST. Primary mutations were detected in 82 % tumor specimens. 66 of them were in KIT, and 16 % in PDGFRA genes. Remaining 18 % were KIT/PDGFRA wild-type. Secondary KIT mutations were detected in 10 from 133 (7 %) patients treated with IM. We examined secondary KIT mutations in exons 13 and 17 and secondary PDGFRA mutation in exon 18 in sixteen progressive tumors and/or metastasis (from overall 22 samples). We identified BRAF V600E point mutation in 4 % of KIT/PDGFRA wild-type GIST patients. Moreover, we analysed SDH complex mutations in 4 younger patients (15, 33, 37, and 45 years old) from 44 patients without KIT, PDGFRA, and BRAF mutations. Two patients (a 37-year old man, and a 33-year old woman) had defects of the SDH complex. Our findings of mutational status of the primary and secondary KIT/PDGFRA mutations in patients with GIST confirm mechanisms of primary and secondary resistance, and also intralesional and interlesional heterogeneity of secondary mutations within and between progressive lesions. Moreover, detection of V600E BRAF mutation and defects of SDH complex in KIT/PDGFRA wild-type GISTs confirm their activation and allow for a selection of targeted therapy.

[Molecular mechanisms of primary and secondary resistance, molecular-genetic features and characteristics of KIT/PDGFRA non-mutated GISTs]. / Molekulární mechanizmy primární a sekundární rezistence, molekulárne-genetické znaky a vlastnosti KIT/PDGFRA nemutovaných GIST.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Most of them arise due to activating mutations in KIT (75 - 85 %) or PDGFRA (less than 10 %) genes. Identification of the activating mutations in KIT and PDGFRA genes, which code for receptor tyrosine kinases (RTKs), has improved the outcome of targeted therapy of metastatic, unresectable or recurrent GISTs. Primary and/or secondary resistance represents a significant problem in the targeted therapy by Imatinib mesylate (IM) in patients with GIST. An important mechanism of the secondary resistance is the evolvement of secondary mutations. Except for primary and secondary resistance, there is another problem of disease progression - a failure of tumor cells eradication even in the long term therapy of tyrosine kinase inhibitors. GISTs without mutations in KIT/PDGFRA genes constitute 10 - 15% GISTs in adults, and a majority (85 %) of pediatric GISTs. KIT/PDGFRA wild-type GISTs represent a heterogeneous group of tumors with several molecular-genetics and/or morphologic differences. KIT/PDGFRA wild-type GISTs are different in their molecular features, for example in mutations in the BRAF, KRAS, NF1 genes or defects of succinate dehydrogenase (SDH) subunits. KIT/PDGFRA wild-type GISTs are generally less sensitive to targeted therapy by tyrosine kinase inhibitors in comparison with KIT/PDGFRA mutated GISTs. Inhibitors of BRAF, PI3K (mTOR) or inhibitors of IGF1R and VEGFR receptors provide alternative therapeutic strategies.

Low predictive value of histopathological scoring system for complications development in children with Crohn's disease.

OBJECTIVES: In pediatric Crohn's disease (PCD), the benefit of microscopy in disease activity assessment and prediction of clinical outcome is, due to the focality and transmurality of the inflammation, disputable. We investigated whether histopathological scoring system predicts complications in pediatric CD and correlates with endoscopical and clinical scores. METHODS: We performed a retrospective study on 63 patients. Endoscopy in the time of diagnosis was evaluated using the Simple Endoscopic Score (SES) and histopathology with the Global Histology Activity Score, both in its original version (GHAS) and its modification (modGHAS). Pediatric Crohn's Disease Activity Index (PCDAI) was also calculated. The patients were grouped according to the presence or absence of defined complications (intraabdominal abscess or fistula, perianal fistulating disease or stricture impenetrable for endoscope or with prestenotic dilatation) during one year of follow-up, or the necessity to initiate anti-TNF treatment for persisting or relapsing active disease in the same time period. Associations were tested with Cox regression analysis. RESULTS: SES was higher in patients with complications. However, in case of GHAS, modGHAS and PCDAI we did not find any significant association with complicated course of disease. SES above 16 points was revealed as an independent risk factor for complications development in PCD, in contrary to GHAS, modGHAS and PCDAI. We demonstrated only a weak correlation between GHAS, modGHAS and SES and no correlation between the histopathological scoring systems and PCDAI. CONCLUSIONS: In conclusion, the histopathological scoring system cannot be recommended as a reliable predictor of development of complications in children with CD.

[A complex diagnostic approach in lymphomas: practical aspect in short case reports]. / Komplexní prístup v diagnostice lymfomu v praktických príkladech.

Complex laboratory investigation is necessary for the diagnosis and relevant classification of lymphomas. The classical histopathological morphology and cytology investigation is essential, but further investigations such as immunohistochemistry and fluorescence in situ hybridization are necessary. It is also important to employ flow cytometry as a method of investigation running synchronously or preceding the histopathological approach. Last but not least, the investigation of nucleic acids in lymphoma by molecular approaches is necessary and has become an everyday practice. Communication between pathologists and clinical colleagues (oncologists, hematologists, internal medicine specialists and radiologists) is very important. We demonstrate the necessity of a complex diagnostic approach to lymphomas and an appropriate interpretation of all laboratory investigations giving examples of eight patients with various types of lymphomas. In some cases, it is impossible to properly diagnose a lymphoma without molecular investigation. Occasionally, the results of the molecular investigation may be misleading and/or may be inaccurately interpreted, leading to an incorrect conclusion. For that reason, it is very important to incorporate all specialized laboratories and their teams under one roof (preferably that of pathology departments), enabling tight and daily cooperation between the specialists. This is the way to reach a precise diagnosis in a majority of cases, as well as how to comply with clinical expectations of properly classified lymphomas for a targeted therapy of patients.