Complexity of PEComas : Diagnostic approach, molecular background, clinical management.

Perivascular epithelioid cell neoplasms (PEComas) are a family of mesenchymal neoplasms with features of both melanotic and smooth muscle differentiation. PEComa morphology is highly variable and encompasses epithelioid to spindle cells often with clear cytoplasm and prominent nucleoli. Molecularly, most PEComas are defined by a loss of function of the TSC1/TSC2 complex. Additionally, a distinct small subset of PEComas harboring rearrangements of the TFE3 (Xp11) gene locus has been identified. By presenting a series of three case reports with distinct features, we demonstrate diagnostic pitfalls as well as the importance of molecular work-up of PEComas because of important therapeutic consequences.

[Microsatellite instability : Review of methods and applications]. / Mikrosatelliteninstabilität : Aktueller Überblick über Methoden und Anwendungen.

After introduction of the Bethesda microsatellite test panel demonstration of microsatellite instability (MSI) and/or loss of mismatch repair proteins (MMRD) was primarily used as a marker for cancer predisposition of Lynch syndrome (LS, previous: HNPCC). Nowadays MSI/MMRD has become an important biomarker to predict therapy response to checkpoint immunotherapies. MSI can be determined either by polymerase chain reaction (PCR)-based technologies with or without specification of fragment sizes or next generation sequencing (NGS) methods. Depending on the individual tumor entities, these test methods are used differently. Currently, MSI/MMRD is a tumor biomarker which covers a broad spectrum of indications in tumor pathology, especially in colorectal, endometrial and gastric cancer. In advanced carcinomas, MSI is an established predictor of therapy response to checkpoint-directed immunotherapies.

[Successful pembrolizumab therapy in metastasized adenosquamous carcinoma of the colon]. / Erfolgreiche Pembrolizumab-Therapie bei metastasiertem adenosquamösem Karzinom des Kolons.

Adenosquamous carcinoma (ASqC) is an exceedingly rare subtype of colorectal cancer without any known special guidelines for treatment. The biological behaviour and molecular background are widely unknown, although a few case studies report a worse prognosis compared to ordinary colorectal adenocarcinoma. We herein report for the first time the successful immune checkpoint inhibitor therapy in a 40-year-old patient suffering from metastasized right-sided colonic ASqC with unique molecular features, after having previously progressed under standard chemotherapy.

[Complexity of PEComas : Diagnostic approach, molecular background, clinical management (German version)]. / Komplexität von PEComen : Diagnose, Molekulargenetik, klinisches Management.

Perivascular epithelioid cell neoplasms (PEComas) are a family of mesenchymal neoplasms with features of both melanotic and smooth muscle differentiation. PEComa morphology is highly variable and encompasses epithelioid to spindle cells often with clear cytoplasm and prominent nucleoli. Molecularly, most PEComas are defined by a loss of function of the TSC1/TSC2 complex. Additionally, a distinct small subset of PEComas harboring rearrangements of the TFE3 (Xp11) gene locus has been identified. By presenting a series of three case reports with distinct features, we demonstrate diagnostic pitfalls as well as the importance of molecular work-up of PEComas because of important therapeutic consequences.

[Molecular diagnostics in neuropathology]. / Molekulare Diagnostik in der Neuropathologie.

As in only few other areas of oncology, molecular markers in neurooncology have become an integral part of clinical decision-making. This development is driven by a bustling scientific activity exploring the molecular basis and pathogenesis of human brain tumors. In addition, a high percentage of brain tumor patients are included in clinical studies in which molecular markers are assessed and linked with clinical informativeness. First steps towards more differentiated therapeutic strategies against brain tumors have thus been taken. The implementation in the clinical and diagnostic routine requires a detailed knowledge and a close collaboration between all medical disciplines involved.

EGFR mutational status in a large series of Caucasian European NSCLC patients: data from daily practice.

BACKGROUND: The prognosis of metastatic non-small cell lung cancer (NSCLC) is still poor. Activating epithelial growth factor receptor (EGFR) mutations are important genetic alterations with dramatic therapeutical implications. Up to now, in contrast to Asian populations only limited data on the prevalence of those mutations are available from patients with Caucasian and especially European ethnicity. METHODS: In this multicentre study, 1201 unselected NSCLC patients from Southern Germany were tested in the daily clinical routine for EGFR mutation status. RESULTS: Activating EGFR mutations were found in 9.8% of all tumours. Mutations in exons 18, 19 and 21 accounted for 4.2%, 61.9% and 33.1% of all mutations, respectively. Non-smokers had a significantly higher rate of EGFR mutations than smokers or ex-smokers (24.4% vs 4.2%; P<0.001). Non-lepidic-non-mucinous adenocarcinomas (G2) accounted for 45.5% of all activating EGFR mutations and 3.5% of all squamous cell carcinomas were tested positive. Thyroid transcription factor 1 protein expression was significantly associated with EGFR mutational status. CONCLUSION: These comprehensive data from clinical routine in Germany add to the knowledge of clinical and histopathological factors associated with EGFR mutational status in NSCLC.

Clinical and molecular practice of European thoracic pathology laboratories during the COVID-19 pandemic. The past and the near future.

BACKGROUND: This study evaluated the consequences in Europe of the COVID-19 outbreak on pathology laboratories orientated toward the diagnosis of thoracic diseases. MATERIALS AND METHODS: A survey was sent to 71 pathology laboratories from 21 European countries. The questionnaire requested information concerning the organization of biosafety, the clinical and molecular pathology, the biobanking, the workload, the associated research into COVID-19, and the organization of education and training during the COVID-19 crisis, from 15 March to 31 May 2020, compared with the same period in 2019. RESULTS: Questionnaires were returned from 53/71 (75%) laboratories from 18 European countries. The biosafety procedures were heterogeneous. The workload in clinical and molecular pathology decreased dramatically by 31% (range, 3%-55%) and 26% (range, 7%-62%), respectively. According to the professional category, between 28% and 41% of the staff members were not present in the laboratories but did teleworking. A total of 70% of the laboratories developed virtual meetings for the training of residents and junior pathologists. During the period of study, none of the staff members with confirmed COVID-19 became infected as a result of handling samples. CONCLUSIONS: The COVID-19 pandemic has had a strong impact on most of the European pathology laboratories included in this study. Urgent implementation of several changes to the organization of most of these laboratories, notably to better harmonize biosafety procedures, was noted at the onset of the pandemic and maintained in the event of a new wave of infection occurring in Europe.

[Microsatellite instability. A new predictive marker (?)]. / Mikrosatelliteninstabilität. Ein neuer prädiktiver Marker (?).

Microsatellite instability (MSI) is a hallmark of hereditary non-polyposis colorectal cancer (HNPCC), but also occurs in about 12%-15% of sporadic colorectal cancer (CRC) where it is a consequence of an epigenetic inactivation of MLH1. High frequency MSI (MSI-H; i.e. at least two of five specified microsatellite markers show instability) was shown in a large meta-analysis and in recent trials to be a positive prognostic marker for overall survival in CRC. MSI-H or mismatch repair deficiency (MMRD) was also shown to be a marker for ineffectiveness of adjuvant 5-fluorouracil (5-FU) based chemotherapy in CRC. At present, there are no guidelines defining the need for microsatellite analysis before chemotherapy. However, studies published to date provide data suggesting that MSI-H CRC patients should not receive adjuvant chemotherapy, with the exception of patients with other factors or poor prognosis (e.g. T4 tumors, G3/G4 status, blood or lymphatic vessel invasion). MSI or MMRD testing can contribute to a more individualized therapy of CRC and should be performed prior to planned 5-FU monotherapy or adjuvant chemotherapy in a non-metastatic setting.

Exploration of the APC/beta-catenin (WNT) pathway and a histologic classification system for pulmonary artery intimal sarcoma. A study of 18 cases.

APC, a tumor suppressor gene in the Wnt pathway, stabilizes beta-catenin and controls cell growth. Mutation of APC or beta-catenin leads to nuclear accumulation of beta-catenin and transcription of cyclin D1/cyclin A. Pulmonary artery sarcoma (PAS) were studied by morphologic, immunohistochemical, and molecular genetic methods of the Wnt pathway. Eighteen cases were included: mean age 52 years, primary intraluminal location with typical clinical presentation. PAS were classified as epithelioid (n = 4) or malignant fibrous histiocytoma (MFH; spindled/pleomorphic, n = 4), myxofibrosarcoma (n = 8), and one each hemangiopericytoma-like or malignant inflammatory myofibroblastic tumor-like. The tumor cells demonstrated vimentin, focal actins, and rare focal desmin positivity. All but one were grade 2 or 3 by FNCLCC grading. Alteration in chromosome 5q21 (APC) was found in 4/14 PAS by LOH, mostly epithelioid-type; an MFH-type case demonstrated microsatellite instability (MSI) and nuclear beta-catenin. Cyclin D1 was expressed in seven tumors, all myxofibrosarcoma-type. No mutations were detected in APC or beta-catenin. In summary, PAS are predominantly intermediate grade myxofibrosarcoma in middle-aged males, and fatal in two-thirds of patients. Despite myofibroblastic phenotype, APC/beta-catenin pathway changes are rare. Cyclin D1, only expressed in the myxofibrosarcoma-type, is likely transcribed via factors other than beta-catenin.

Diagnostic microsatellite instability: definition and correlation with mismatch repair protein expression.

Alterations of the length of simple repetitive genomic sequences (microsatellite instability, MSI) characterize a distinct mechanism of colorectal carcinogenesis. Such MSI has been found to be associated with hereditary nonpolyposis colorectal cancer (HNPCC) that involves mutation of the human mismatch repair genes hMSH2 and hMLH1 as well as many sporadic cancers of most tissue types. Although the study of MSI status is a useful tool for HNPCC screening and for the determination of tumor prognosis in sporadic cases of colorectal cancer, the reliability of MSI diagnosis is still a subject of debate. Here we have examined 58 primary colorectal tumors (selected from a cohort of 200) using 31 microsatellite markers that comprised the most frequent simple repeat types. The expression of the hMSH2 and hMLH1 mismatch repair proteins was studied by immunohistochemistry, and most patients were surveyed for at least 2 years. Reproducibility of gel interpretation, as well as diagnostic sensitivity and specificity of the MSI status, were determined. We found that unambiguous determination of band shifts as well as MSI diagnosis were closely related to the type of the marker repeat and that MSI could be subdivided into "high" MSI (>20% unstable loci), "low" MSI (<10% unstable loci), and microsatellite stable (0% unstable loci). One-half of the patients with high MSI tumors (n = 8) fulfilled either the Amsterdam criteria (n = 4), had at least one relative with HNPCC-related carcinoma (n = 2), or were diagnosed with colorectal cancer at an age below 45 years (n = 2). Fourteen of the 15 high MSI tumors had lost either hMSH2 (n = 8) or hMLH1 (n = 6) protein expression. In contrast, all of the low MSI tumors and the MSI-negative tumors displayed normal expression of hMSH2 and hMLH1. These studies provide a clear recommendation for the uniform use of a panel of 10 microsatellites and a definition of at least 40% instability (using these defined marker loci) in the diagnostic analysis of MSI.

Evidence for oligoclonality and tumor spread by intraluminal seeding in multifocal urothelial carcinomas of the upper and lower urinary tract.

Multifocality and recurrence of urothelial carcinoma may result from either the field effect of carcinogens leading to oligoclonal tumors or monoclonal tumor spread. Previous molecular studies, favoring the monoclonality hypothesis, are mostly limited to the urinary bladder. We investigated genetic alterations in a total of 94 synchronous or metachronous multifocal tumors from 19 patients with at least one tumor both in the upper and lower urinary tract. Loss of heterozygosity (LOH) was determined using eight markers on chromosome 9 and one marker on 17p13 (p53). Microsatellite instability was investigated at six loci and protein expression of MSH2 and MLH1 was evaluated by immunohistochemistry. In addition, exons 5-9 of the p53 gene were sequenced. Deletions at chromosome 9 were found in 73% of tumors and at 17p13 in 18% of tumors. There was no significant difference in the frequency of LOH in the upper and lower urinary tract. Deletions at 9p21 were significantly correlated with invasive tumor growth. The pattern of deletion revealed monoclonality of all tumors in nine patients. In five patients there were at least two tumor clones with different genetic alterations. In four of these patients the different clones occurred in the bladder and subsequently in the ureter and renal pelvis. All four patients with p53 mutations revealed identical mutations in all tumors. Thus, multifocal urothelial carcinomas are frequently monoclonal, whereas others show oligoclonality, providing molecular evidence for field cancerization. Intraluminal tumor cell seeding appears to be an important mechanism of multifocal occurrence and recurrence of urothelial carcinomas.