Overall survival and central nervous system activity of crizotinib in ROS1-rearranged lung cancer-final results of the EUCROSS trial.

BACKGROUND: In 2019, we reported the first efficacy and safety analysis of EUCROSS, a phase II trial investigating crizotinib in ROS1 fusion-positive lung cancer. At that time, overall survival (OS) was immature and the effect of crizotinib on intracranial disease control remained unclear. Here, we present the final analysis of OS, systemic and intracranial activity, and the impact of co-occurring aberrations. MATERIALS AND METHODS: EUCROSS was a prospective, single-arm, phase II trial. The primary endpoint was best overall response rate (ORR) using RECIST 1.1. Secondary and exploratory endpoints were progression-free survival (PFS), OS, and efficacy in pre-defined subgroups. RESULTS: Median OS of the intention-to-treat population (N = 34) was 54.8 months [95% confidence interval (CI) 20.3 months-not reached (NR); median follow-up 81.4 months] and median all-cause PFS of the response-evaluable population (N = 30) was 19.4 months (95% CI 10.1-32.2 months). Time on treatment was significantly correlated with OS (R = 0.82; P < 0.0001). Patients with co-occurring TP53 aberrations (28%) had a significantly shorter OS [hazard ratio (HR) 11; 95% CI 2.0-56.0; P = 0.006] and all-cause PFS (HR 4.2; 95% CI 1.2-15; P = 0.025). Patients with central nervous system (CNS) involvement at baseline (N = 6; 20%) had a numerically shorter median OS and all-cause PFS. Median intracranial PFS was 32.2 months (95% CI 23.7 months-NR) and the rate of isolated CNS progression was 24%. CONCLUSIONS: Our final analysis proves the efficacy of crizotinib in ROS1-positive lung cancer, but also highlights the devastating impact of TP53 mutations on survival and treatment efficacy. Additionally, our data show that CNS disease control is durable and the risk of CNS progression while on crizotinib treatment is low.

Treatment outcome of atypical EGFR mutations in the German National Network Genomic Medicine Lung Cancer (nNGM).

BACKGROUND: Atypical EGFR mutations occur in 10%-30% of non-small-cell lung cancer (NSCLC) patients with EGFR mutations and their sensitivity to classical epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKI) is highly heterogeneous. Patients harboring one group of uncommon, recurrent EGFR mutations (G719X, S768I, L861Q) respond to EGFR-TKI. Exon 20 insertions are mostly insensitive to EGFR-TKI but display sensitivity to exon 20 inhibitors. Clinical outcome data of patients with very rare point and compound mutations upon systemic treatments are still sparse to date. PATIENTS AND METHODS: In this retrospective, multicenter study of the national Network Genomic Medicine (nNGM) in Germany, 856 NSCLC cases with atypical EGFR mutations including co-occurring mutations were reported from 12 centers. Clinical follow-up data after treatment with different EGFR-TKIs, chemotherapy and immune checkpoint inhibitors were available from 260 patients. Response to treatment was analyzed in three major groups: (i) uncommon mutations (G719X, S7681, L861Q and combinations), (ii) exon 20 insertions and (iii) very rare EGFR mutations (very rare single point mutations, compound mutations, exon 18 deletions, exon 19 insertions). RESULTS: Our study comprises the largest thus far reported real-world cohort of very rare EGFR single point and compound mutations treated with different systemic treatments. We validated higher efficacy of EGFR-TKI in comparison to chemotherapy in group 1 (uncommon), while most exon 20 insertions (group 2) were not EGFR-TKI responsive. In addition, we found TKI sensitivity of very rare point mutations (group 3) and of complex EGFR mutations containing exon 19 deletions or L858R mutations independent of the combination partner. Notably, treatment responses in group 3 (very rare) were highly heterogeneous. Co-occurring TP53 mutations exerted a non-significant trend for a detrimental effect on outcome in EGFR-TKI-treated patients in groups 2 and 3 but not in group 1. CONCLUSIONS: Based on our findings, we propose a novel nNGM classification of atypical EGFR mutations.

[Homologous recombination repair deficiency as a predictive biomarker : Basic mechanisms and detection methods]. / Defizienz der homologen Rekombinationsreparatur als prädiktiver Marker : Grundlagen und Nachweis.

BACKGROUND: DNA double-strand breaks may evoke cell death or cancer. Cells have developed two fundamentally different mechanisms of DNA double-strand repair: the accurate mechanism of homologous recombination repair and the error-prone nonhomologous end joining. The deficiency of homologous recombination repair (HRD) is a frequent feature of several solid tumor entities and is associated with sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitor therapy. OBJECTIVES: Among other biomarkers, HRD testing provides an opportunity to guide PARP inhibitor therapy in solid tumors, but the basic principles are complex and the use and benefits of the different methodologies remain controversial. Knowledge of the underlying mechanisms at the molecular level will advance our understanding and will pave the way to introduce the testing of new biomarkers. METHODS: An overview of the fundamental mechanisms of DNA repair is provided. Important terms like HRR, HRD, and BRCAness are defined, and analysis methods are described, especially with regard to their integration in molecular pathology routine diagnostics. RESULTS: Currently, at least testing of the BRCA mutation status and genomic instability using a composite HRD score should be implemented in laboratories to identify subgroups of patients who might benefit from PARP inhibitor therapies. A broad range of testing methods is available with pros and cons for introduction in the clinical setting. They have to be validated carefully to reliably inform treatment selection. CONCLUSIONS: Biomarkers to identify current homologous recombination deficiency status are needed to predict the benefit from PARP inhibitors and stratify their use in clinical management. Besides commercial assays, different tests might be used for the analysis of HRD. The application depends, among other things, on the local situation and has to be extensively validated.

GNAQ and GNA11 mutant nonuveal melanoma: a subtype distinct from both cutaneous and uveal melanoma.

BACKGROUND: GNAQ and GNA11 mutant nonuveal melanoma represent a poorly characterized rare subgroup of melanoma with a gene mutation profile similar to uveal melanoma. OBJECTIVES: To characterize these tumours in terms of clinical behaviour and genetic characteristics. METHODS: Patients with nonuveal GNAQ/11 mutated melanoma were identified from the prospective multicentre tumour tissue registry ADOREG, Tissue Registry in Melanoma (TRIM) and additional cooperating skin cancer centres. Extensive data on patient, tumour and treatment characteristics were collected retrospectively. Targeted sequencing was used to determine tumour mutational burden. Immunohistochemistry staining was performed for programmed death-ligand 1 and BRCA1-associated protein (BAP)1. Existing whole-exome cutaneous and uveal melanoma data were analysed for mutation type and burden. RESULTS: We identified 18 patients with metastatic GNAQ/11 mutant nonuveal melanoma. Tumours had a lower tumour mutational burden and fewer ultraviolet signature mutations than cutaneous melanomas. In addition to GNAQ and GNA11 mutations (nine each), six splicing factor 3b subunit 1 (SF3B1), three eukaryotic translation initiation factor 1A X-linked (EIF1AX) and four BAP1 mutations were detected. In contrast to uveal melanoma, GNAQ/11 mutant nonuveal melanomas frequently metastasized lymphatically and concurrent EIF1AX, SF3B1 and BAP1 mutations showed no apparent association with patient prognosis. Objective response to immunotherapy was poor with only one partial response observed in 10 treated patients (10%). CONCLUSIONS: Our findings suggest that GNAQ/11 mutant nonuveal melanomas are a subtype of melanoma that is both clinically and genetically distinct from cutaneous and uveal melanoma. As they respond poorly to available treatment regimens, novel effective therapeutic approaches for affected patients are urgently needed. What is already known about this topic? The rare occurrence of GNAQ/11 mutations in nonuveal melanoma has been documented. GNAQ/11 mutant nonuveal melanomas also harbour genetic alterations in EIF1AX, SF3B1 and BAP1 that are of prognostic relevance in uveal melanoma. What does this study add? GNAQ/11 mutant nonuveal melanomas show metastatic spread reminiscent of cutaneous melanoma, but not uveal melanoma. GNAQ/11 mutant nonuveal melanomas have a low tumour mutational burden that is higher than uveal melanoma, but lower than cutaneous melanoma. What is the translational message? Primary GNAQ/11 mutant nonuveal melanomas are a subtype of melanoma that is clinically and genetically distinct from both cutaneous and uveal melanoma. As metastatic GNAQ/11 mutant nonuveal melanomas respond poorly to available systemic therapies, including immune checkpoint inhibition, novel therapeutic approaches for these tumours are urgently needed. Linked Comment: Rafei-Shamsabadi. Br J Dermatol 2020; 183:806-807.

[Status of the availability and use of next generation sequencing (NGS) in bladder cancer-a questionnaire within the uropathology working group]. / Status der Verfügbarkeit und Anwendung von "next generation sequencing" (NGS) beim Harnblasenkarzinom ­ eine Umfrage in der Arbeitsgemeinschaft Uropathologie.

BACKGROUND: Technical advancement and availability of high-throughput analysis has advanced molecular subtyping of most cancers. Thus, new possibilities for precision oncology have emerged. AIM: Therefore, we aimed to collect data regarding availability and use of next generation sequencing (NGS) for urothelial cancer within the uropathology working group of the German Society of Pathology. METHODS: We collected data by questionnaires and additionally asked for sequencing results of bladder cancers in the participating institutions. RESULTS: A total of 13 university-affiliated institutes of pathology took part in the survey. All university institutes offer NGS-based molecular panel diagnostics and provide panels covering between 15 and 170 genes. Altogether, only 20 bladder cancers were sequenced in routine diagnostics and for 10 cancers potential targeted treatment options were available. DISCUSSION: So far, despite availability of NGS diagnostics at university institutes of pathology, only few bladder cancer samples have been sequenced. Based on current data from the molecular subtyping of bladder cancers, we recommend a step-by-step protocol with basic immunohistochemistry analysis and subsequent subtype-dependent analyses, e.g., alterations of the fibroblast growth factor receptors (FGFR) or comprehensive gene panel analyses.

Impact of TP53 mutation status on systemic treatment outcome in ALK-rearranged non-small-cell lung cancer.

Background: We analyzed whether co-occurring mutations influence the outcome of systemic therapy in ALK-rearranged non-small-cell lung cancer (NSCLC). Patients and methods: ALK-rearranged stage IIIB/IV NSCLC patients were analyzed with next-generation sequencing and fluorescence in situ hybridization analyses on a centralized diagnostic platform. Median progression-free survival (PFS) and overall survival (OS) were determined in the total cohort and in treatment-related sub-cohorts. Cox regression analyses were carried out to exclude confounders. Results: Among 216 patients with ALK-rearranged NSCLC, the frequency of pathogenic TP53 mutations was 23.8%, while other co-occurring mutations were rare events. In ALK/TP53 co-mutated patients, median PFS and OS were significantly lower compared with TP53 wildtype patients [PFS 3.9 months (95% CI: 2.4-5.6) versus 10.3 months (95% CI: 8.6-12.0), P < 0.001; OS 15.0 months (95% CI: 5.0-24.9) versus 50.0 months (95% CI: 22.9-77.1), P = 0.002]. This difference was confirmed in all treatment-related subgroups including chemotherapy only [PFS first-line chemotherapy 2.6 months (95% CI: 1.3-4.1) versus 6.2 months (95% CI: 1.8-10.5), P = 0.021; OS 2.0 months (95% CI: 0.0-4.6) versus 9.0 months (95% CI: 6.1-11.9), P = 0.035], crizotinib plus chemotherapy [PFS crizotinib 5.0 months (95% CI: 2.9-7.2) versus 14.0 months (95% CI: 8.0-20.1), P < 0.001; OS 17.0 months (95% CI: 6.7-27.3) versus not reached, P = 0.049] and crizotinib followed by next-generation ALK-inhibitor [PFS next-generation inhibitor 5.4 months (95% CI: 0.1-10.7) versus 9.9 months (95% CI: 6.4-13.5), P = 0.039; OS 7.0 months versus 50.0 months (95% CI: not reached), P = 0.001). Conclusions: In ALK-rearranged NSCLC co-occurring TP53 mutations predict an unfavorable outcome of systemic therapy. Our observations encourage future research to understand the underlying molecular mechanisms and to improve treatment outcome of the ALK/TP53 co-mutated subgroup.

Therapy susceptible germline-related BRCA 1-mutation in a case of metastasized mixed adeno-neuroendocrine carcinoma (MANEC) of the small bowel.

BACKGROUND: Adenocarcinomas or combined adeno-neuroendocrine carcinomas (MANEC) of small bowel usually have a dismal prognosis with limited systemic therapy options. This is the first description of a patient showing a germline-related BRCA1 mutated MANEC of his ileum. The tumor presented a susceptibility to a combined chemotherapy and the PARP1-inhibitor olaparib. CASE PRESENTATION: A 74-year old male patient presented with a metastasized MANEC of his ileum. Due to clinical symptoms his ileum-tumor and the single brain metastasis were removed. We verified the same pathogenic (class 5) BRCA1 mutation in different tumor locations. There was no known personal history of a previous malignant tumor. Nevertheless we identified his BRCA1 mutation as germline-related. A systemic treatment was started including Gemcitabine followed by selective internal radiotherapy (SIRT) to treat liver metastases and in the further course Capecitabine but this treatment finally failed after 9 months and all liver metastases showed progression. The treatment failure was the reason to induce an individualized therapeutic approach using combined chemotherapy of carboplatin, paclitaxel and the Poly (ADP-ribose) polymerase- (PARP)-inhibitor olaparib analogous to the treatment protocol of Oza et al. All liver metastases demonstrated with significant tumor regression after 3 months and could be removed. In his most current follow up from December 2017 (25 months after his primary diagnosis) the patient is in a very good general condition without evidence for further metastases. CONCLUSION: We present first evidence of a therapy susceptible germline-related BRCA1 mutation in small bowel adeno-neuroendocrine carcinoma (MANEC). Our findings offer a personalized treatment option. The germline background was unexpected in a 74-year old man with no previously known tumor burden. We should be aware of the familiar background in tumors of older patients as well.

ALK evaluation in the world of multiplex testing: Network Genomic Medicine (NGM): the Cologne model for implementing personalised oncology.

Comprehensive molecular genotyping of lung cancers has become a key requirement for guiding therapeutic decisions. As a paradigm model of implementing next-generation comprehensive diagnostics, Network Genomic Medicine (NGM) has established central diagnostic and clinical trial platforms for centralised testing and decentralised personalised treatment in clinical practice. Here, we describe the structures of the NGM network and give a summary of technologies to identify patients with anaplastic lymphoma kinase (ALK) fusion-positive lung adenocarcinomas. As unifying test platforms will become increasingly important for delivering reliable, quick and affordable tests, the NGM diagnostic platform is currently implementing a comprehensive hybrid capture-based parallel sequencing pan-cancer assay.

Assessment of clinical parameters associated with mutational status in metastatic malignant melanoma: a single-centre investigation of 141 patients.

BACKGROUND: Inhibitors of the mutated, constitutively activated BRAF protein have shown efficacy in the treatment of metastatic melanoma in clinical trials. Mutation analysis especially of the BRAF, NRAS and KIT genes is essential to identify patients suitable for targeted therapies and has been introduced into routine patient care. OBJECTIVES: To correlate mutational status with clinical parameters including age, skin type, number of melanocytic naevi, primary tumour location, chronic sun damage and exposure to ultraviolet (UV) irradiation. The overall aim was to define subgroups with an increased or decreased likelihood of gene mutations. Additionally, the impact of activating BRAF mutations on clinical course was investigated. METHODS: In a single-centre, retrospective approach, mutation analysis was performed on patients with metastatic malignant melanoma. Clinical parameters were correlated with molecular findings. The total sun-burden score was assessed using a validated standardized questionnaire. RESULTS: The analysis included 141 patients with metastatic melanoma. Forty-four per cent of patients had activating BRAF mutations and were significantly younger than patients with wild-type BRAF or with NRAS mutations. KIT mutations were detected in only 3% of the patients. BRAF-mutated melanomas developed preferentially in intermittently sun-exposed areas of the body, and patients had significantly more melanocytic naevi. Once patients had progressed into stage IV disease, survival times were identical for those with BRAF-mutated and BRAF wild-type tumours. CONCLUSIONS: Mutations of the BRAF gene are correlated with younger age, a higher number of melanocytic naevi and a tumour location in intermittently UV-exposed skin. Signs of chronic photodamage are not indicative of mutational status. Patients with metastatic melanoma with BRAF mutations showed a nonsignificant tendency to progress later to stage IV disease, but once metastases were present the prognosis was identical to that with BRAF wild-type tumours.

[Are sarcoma centers needed in Germany? Experience gained with the Bonner GIST register]. / Brauchen wir in Deutschland Sarkomzentren? Erfahrungen aus dem Bonner GIST-Register.

Due to their rarity and multiple subtypes, there is scant experience with sarcomas. Any effective targeted therapy depends on precise diagnosis of the tumor group using molecular markers and, increasingly, mutation testing. The necessary histopathological expertise and molecular diagnostic tools are usually only found at specialized centers. Using the Bonner GIST register as an example, the advantages of this kind of register from a diagnostic and therapeutic perspective will be discussed. Material submitted for gastrointestinal stromal tumors and other mesenchymal tumors, as well as the supervision of pathological referencing for national and international studies have made accurate diagnosis and appropriate therapy strategies ever more possible. The introduction of epidemiological as well as interdisciplinary sarcoma registers is a prerequisite for the improvement of sarcoma diagnostics and therapy.

[Molecular methods in the diagnosis of sarcoma]. / Molekulare Methoden in der Sarkomdiagnostik.

The use of modern molecular techniques has gained importance in the diagnosis of sarcomas in recent years. Each of the analytical methods discussed here has its unique advantages and specific requirements. Cytogenetic screening methods which provide genome-wide information depend on the availability of fresh tissue. With the aid of fluorescence in situ hybridization and RT-polymerase chain reaction, specific events such as translocations in Ewing sarcoma, synovial sarcoma or alveolar rhabdomyosarcoma, as well as gene amplifications in well-differentiated and dedifferentiated liposarcoma or radiation-induced angiosarcoma and deletions in rhabdoid tumors or well-differentiated spindle cell liposarcoma can be detected in fresh and formalin fixed tissues. Molecular methods including Sanger sequencing, pyrosequencing and high resolution melting provide information about specific molecular aberrations on gene level. Here we review the most important molecular techniques currently used in sarcoma diagnosis, describe their relevance for differential diagnosis and point out specific examples.

Soft tissue sarcoma: from molecular diagnosis to selection of treatment. Pathological diagnosis of soft tissue sarcoma amid molecular biology and targeted therapies.

During the past few years, differential diagnosis of soft tissue tumours has improved due to novel molecular diagnostic tools. Besides a better differentiation between different tumour entities the recognition of specific molecular aberrations may also help to identify novel therapeutic targets. One of the most promising examples of effective molecularly driven treatment is the gastrointestinal stromal tumour. Shortly after the detection of gain-of-function mutations in the type III receptor tyrosine kinases KIT and PDGFRα a targeted treatment with the tyrosine kinase inhibitor imatinib was introduced and became the gold standard in advanced GIST disease. The success of this therapy with response rates of >80% stable disease and partial remission is still unmatched. Since then, many groups aim to identify other potential molecular targets. Genomic and proteomic signatures may pinpoint potential areas of interest for diagnostic tools, prediction of clinical outcome and potential response to therapeutic targets. This article gives an overview of the most important genomic aberrations in sarcomas, their differential diagnosis and the relevance of molecular biology for treatment strategies.

[Gastrointestinal stromal tumors of the stomach. Updates and differences compared to other locations]. / Gastrointestinale Stromatumoren des Magens. Neues und Besonderes im Vergleich zu anderen Lokalisationen.

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumors of the gastrointestinal tract. Two thirds of them are located in the stomach, another 30% occur in the small bowel, while the remaining tumors occur in the rectum or more rarely in the oesophagus. GIST most commonly grow from the smooth muscular layer towards the serosal surface whereas development towards to the mucosal layer is less frequent. In the latter case ulceration may occur, leading to gastrointestinal bleeding as the main symptom. However, the majority of GIST of the stomach are asymptomatic, resulting in large tumors on initial diagnosis. Most gastric GIST are not visible on endoscopy but may be diagnosed by endosonography. Due to their location in the outer layers of the tubular gastrointestinal tract biopsy is often hindered of even impossible. GIST of the stomach differ from tumors in other locations with regard to their morphology, molecular pathology and prognosis. This present article provides an overview of these differences also with regard to possible therapeutic consequences.

[Inflammatory fibroid polyp: from Vanek's "submucosal granuloma" to the concept of submucosal mesenchymal neoplasia]. / Inflammatorischer fibroider Polyp: Von Vaneks "submukösem Granulom" zum Konzept einer submukösen mesenchymalen Neoplasie.

Inflammatory fibroid polyps (IFP) were described by Vanek 60 years ago as "submucosal granuloma with eosinophilic infiltration". IFP represent polypous proliferations of spindle cells in the submucosa and mucosa of the stomach, small bowel and colon with inflammatory infiltration. The lesions have been regarded as inflammatory and reactive. Recent data show that the spindle cells express PDGFRA, and the majority of IFP harbour activating PDGFRA mutations. Therefore, IFP represent true benign mesenchymal tumors of the gastrointestinal tract.

[Inflammatory fibroid polyps are true neoplasms with PDGFRA mutations]. / Inflammatorische fibroide Polypen sind echte Neoplasien mit PDGFRA-Mutationen.

AIMS: Inflammatory fibroid polyps (IFP) are proliferations of CD34-positive spindle cells in the submucosa and mucosa of the gastrointestinal tract with an inflammatory infiltrate. IFP occur in the stomach, small bowel, colon and esophagus. To date, etiology and pathogenesis are unclear. METHODS: A total of 29 IFP originating in the stomach, small bowel and colon were examined immunohistochemically, and mutational analyses of PDGFRA exons 10, 12, 14 and 18 were conducted. RESULTS: Activating mutations in PDGFRA exons 12 and 18 were found in 20 cases (69%). The mutational types are related to mutations known from gastrointestinal stromal tumors (GIST). D842V was the most frequent mutation. No activating mutations were found in exons 10 and 14. CONCLUSIONS: The majority of IFP reveal activating PDGFRA mutations. Our data indicate that IFP are true neoplasms (true benign tumors) and not reactive lesions. In terms of pathogenesis, the relationship between PDGFRA-mutant GISTs and IFP remains to be determined.

[Pathology and molecular biology of gastrointestinal stromal tumors (GIST)]. / Pathologie und Molekularbiologie gastrointestinaler Stromatumoren (GIST).

Gastrointestinal stromal tumors (GIST) show an aggressive behavior with metastases and recurrences in up to 50% of cases. They can be clearly distinguished from other mesenchymal tumors by immunohistochemistry in the vast majority of cases. Of the tumors 85% carry somatic activating mutations in the receptor tyrosine kinases KIT or PDGFRA. The detection of these molecular events has changed the treatment of inoperable and metastatic GISTs dramatically as up to 80% of tumors respond well to tyrosine kinase inhibitors. This treatment has become the gold standard in the last few years with only few side effects. Knowledge of the underlying KIT or PDGFRA mutation is both relevant for the prognosis and treatment response.

Nuclear hBD-1 accumulation in malignant salivary gland tumours.

BACKGROUND: Whereas the antimicrobial peptides hBD-2 and -3 are related to inflammation, the constitutively expressed hBD-1 might function as 8p tumour suppressor gene and thus play a key role in control of transcription and induction of apoptosis in malignant epithelial tumours. Therefore this study was conducted to characterise proteins involved in cell cycle control and host defence in different benign and malignant salivary gland tumours in comparison with healthy salivary gland tissue. METHODS: 21 paraffin-embedded tissue samples of benign (n = 7), and malignant (n = 7) salivary gland tumours as well as healthy (n = 7) salivary glands were examined immunohistochemically for the expression of p53, bcl-2, and hBD-1, -2, -3. RESULTS: HBD-1 was distributed in the cytoplasm of healthy salivary glands and benign salivary gland tumours but seems to migrate into the nucleus of malignant salivary gland tumours. Pleomorphic adenomas showed cytoplasmic as well as weak nuclear hBD-1 staining. CONCLUSION: HBD-1, 2 and 3 are traceable in healthy salivary gland tissue as well as in benign and malignant salivary gland tumours. As hBD-1 is shifted from the cytoplasm to the nucleus in malignant salivary gland tumours, we hypothesize that it might play a role in the oncogenesis of these tumours. In pleomorphic adenomas hBD-1 might be connected to their biologic behaviour of recurrence and malignant transformation.

Inflammatory fibroid polyps harbour mutations in the platelet-derived growth factor receptor alpha (PDGFRA) gene.

Inflammatory fibroid polyps (IFPs) are mesenchymal tumours which arise in the submucosa and mucosa of the gastrointestinal tract. To date, the pathogenesis is unknown and IFPs are considered reactive and non-neoplastic lesions. Investigating a series of 23 IFPs, we made the observation that the tumours consistently express PDGFRA. To further elucidate the pathogenetic role of PDGFRA, we performed mutational analyses of exons 10, 12, 14, and 18. As IFPs are characterized by an inflammatory infiltrate rich in eosinophils, we used fluorescence in situ hybridization in a subset of tumours to investigate a possible FIP1L1-PDGFRA translocation which is known as the cause of hypereosinophilic syndrome (HES). Sixteen IFPs (70%) harboured activating mutations in exons 12 and 18, respectively: V561D (n = 1), R560SDelta561-567 (n = 1), Delta559-561D591H (n = 1), S566RDelta567-571 (n = 3), D842V (n = 7), D842I (n = 1), Delta842-845 (n = 1), and Delta845-848 (n = 1). These mutations equal pathogenic mutations detected in gastrointestinal stromal tumours previously. Activating mutations in exons 10 and 14 were not noted. None of the cases revealed the FIP1L1-PDGFRA translocation. Considering the remarkable number of activating mutations detected in our series, we conclude that the vast majority of IFPs harbour gain-of-function mutations in the PDGFRA gene. The presence of PDGFRA mutations questions the reactive nature of IFPs and raises the possibility of a neoplastic process.

RNA-based mutation analysis identifies an unusual MSH6 splicing defect and circumvents PMS2 pseudogene interference.

Heterozygous germline mutations in one of the mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2 cause hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome, a dominantly inherited cancer susceptibility syndrome. Recent reports provide evidence for a novel recessively inherited cancer syndrome with constitutive MMR deficiency due to biallelic germline mutations in one of the MMR genes. MMR-deficiency (MMR-D) syndrome is characterized by childhood brain tumors, hematological and/or gastrointestinal malignancies, and signs of neurofibromatosis type 1 (NF1). We established an RNA-based mutation detection assay for the four MMR genes, since 1) a number of splicing defects may escape detection by the analysis of genomic DNA, and 2) DNA-based mutation detection in the PMS2 gene is severely hampered by the presence of multiple highly similar pseudogenes, including PMS2CL. Using this assay, which is based on direct cDNA sequencing of RT-PCR products, we investigated two families with children suspected to suffer from MMR-D syndrome. We identified a homozygous complex MSH6 splicing alteration in the index patients of the first family and a novel homozygous PMS2 mutation (c.182delA) in the index patient of the second family. Furthermore, we demonstrate, by the analysis of a PMS2/PMS2CL "hybrid" allele carrier, that RNA-based PMS2 testing effectively avoids the caveats of genomic DNA amplification approaches; i.e., pseudogene coamplification as well as allelic dropout, and will, thus, allow more sensitive mutation analysis in MMR deficiency and in HNPCC patients with PMS2 defects.