Smaller panel, similar results: genomic profiling and molecularly informed therapy in pancreatic cancer

BACKGROUND

Pancreatic cancer has a dismal prognosis. One reason is resistance to cytotoxic drugs. Molecularly matched therapies might overcome this resistance but the best approach to identify those patients who may benefit is unknown. Therefore, we sought to evaluate a molecularly guided treatment approach.

MATERIALS AND METHODS

We retrospectively analyzed the clinical outcome and mutational status of patients with pancreatic cancer who received molecular profiling at the West German Cancer Center Essen from 2016 to 2021. We carried out a 47-gene DNA next-generation sequencing (NGS) panel. Furthermore, we assessed microsatellite instability-high/deficient mismatch repair (MSI-H/dMMR) status and, sequentially and only in case of KRAS wild-type, gene fusions via RNA-based NGS. Patient data and treatment were retrieved from the electronic medical records.

RESULTS

Of 190 included patients, 171 had pancreatic ductal adenocarcinoma (90%). One hundred and three patients had stage IV pancreatic cancer at diagnosis (54%). MMR analysis in 94 patients (94/190, 49.5%) identified 3 patients with dMMR (3/94, 3.2%). Notably, we identified 32 patients with KRAS wild-type status (16.8%). To identify driver alterations in these patients, we conducted an RNA-based fusion assay on 13 assessable samples and identified 5 potentially actionable fusions (5/13, 38.5%). Overall, we identified 34 patients with potentially actionable alterations (34/190, 17.9%). Of these 34 patients, 10 patients (10/34, 29.4%) finally received at least one molecularly targeted treatment and 4 patients had an exceptional response (>9 months on treatment).

CONCLUSIONS

Here, we show that a small-sized gene panel can suffice to identify relevant therapeutic options for pancreatic cancer patients. Informally comparing with previous large-scale studies, this approach yields a similar detection rate of actionable targets. We propose molecular sequencing of pancreatic cancer as standard of care to identify KRAS wild-type and rare molecular subsets for targeted treatment strategies.

Multimodal survival prediction in advanced pancreatic cancer using machine learning

Background

Existing risk scores appear insufficient to assess the individual survival risk of patients with advanced pancreatic ductal adenocarcinoma (PDAC) and do not take advantage of the variety of parameters that are collected during clinical care.

Methods

In this retrospective study, we built a random survival forest model from clinical data of 203 patients with advanced PDAC. The parameters were assessed before initiation of systemic treatment and included age, CA19-9, C-reactive protein, metastatic status, neutrophil-to-lymphocyte ratio and total serum protein level. Separate models including imaging and molecular parameters were built for subgroups.

Results

Over the entire cohort, a model based on clinical parameters achieved a c-index of 0.71. Our approach outperformed the American Joint Committee on Cancer (AJCC) staging system and the modified Glasgow Prognostic Score (mGPS) in the identification of high- and low-risk subgroups. Inclusion of the KRAS p.G12D mutational status could further improve the prediction, whereas radiomics data of the primary tumor only showed little benefit. In an external validation cohort of PDAC patients with liver metastases, our model achieved a c-index of 0.67 (mGPS: 0.59).

Conclusions

The combination of multimodal data and machine-learning algorithms holds potential for personalized prognostication in advanced PDAC already at diagnosis.

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We developed a machine-learning-based prediction model that outperforms the AJCC staging system and mGPS.

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Applying our model to an external validation cohort demonstrates generalizability.

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Explainable machine learning enables to understand the decision making of our model and identifies relevant parameters.

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Combining clinical, imaging and genetic data holds potential for personalized prognostication in advanced PDAC.

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 NSCLC patients with EGFR mutations and their sensitivity to classical 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, multi-center study of the national Network Genomic Medicine (nNGM) in Germany, 856 NSCLC cases with atypical EGFR mutations including co-occuring mutations were reported from 12 centers. Clinical follow-up data after treatment with different EGFR-TKI, chemotherapy and immune checkpoint inhibitors were available from 260 patients. Response to treatment was analyzed in three major groups: (1) uncommon mutations (G719X, S7681, L861Q and combinations), (2) exon 20 insertions and (3) 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 uncommon EGFR mutations.

DLL3 (delta-like protein 3) expression correlates with stromal desmoplasia and lymph node metastases in medullary thyroid carcinomas

Medullary thyroid carcinomas (MTC) are rare and aggressive neuroendocrine tumors of the thyroid. About 70% of MTC are sporadic; approximately 50% of those harbor somatic RET mutation. DLL3 is widely expressed in many neuroendocrine tumors and has been evaluated as a potential therapeutic target. Since stromal desmoplasia in sporadic MTC has been identified as a reliable predictor of aggressive behavior and development of lymph node metastases, a possible correlation of DLL3 expression with the presence of stromal desmoplasia was of particular interest. 59 paraffin-embedded samples of sporadic MTC with (44 cases) and without (15 cases) stromal desmoplasia and known lymph node status were included. DLL3 expression was determined by immunohistochemistry; no expression (0%), low expression (1-49%) and high expression (≥50%) were correlated with clinicopathological data. The proportion of DLL3 positivity was significantly correlated with both stromal desmoplasia (P < 0.0001) and lymph node metastases (P < 0.0001). MTC without stromal desmoplasia consistently lack DLL3 expression. This is the first study to focus on MTC regarding DLL3 expression and the relationship to various factors. Our results demonstrate that expression of DLL3 in MTC represents a reliable surrogate marker for stromal desmoplasia and lymph node metastases and might be an indicator for aggressive clinical behavior. DLL3 expression in ≥50% of tumor cells virtually excludes MTC without stromal desmoplasia. DLL3 was discussed as a potential therapeutic target in malignant tumors of other locations with positive immunohistochemical reaction and might therefore be a new therapeutic option in MTC, as well.

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.

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Biosafety measures used in the first wave of the COVID-19 crisis were heterogeneous in 53 European pathology laboratories.

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A dramatic decrease of the workload in pathology laboratories was noted.

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No case of healthcare workers contaminated with SARS-CoV-2 associated with samples handling was identified.

[Predictive value of PD-L1 diagnostics]

Immuno-oncology related treatments have become standard of care for many tumor entities. Numerous additional indications are currently under investigation in ongoing clinical trials. Predictive biomarkers include microsatellite instability as well as tumor mutational burden. However, PD-L1 testing by immunohistochemistry (IHC) is already widely established as a biomarker in clinical routine for certain treatment decisions in non-small cell lung cancer, head and neck cancer and in urothelial carcinomas. More applications of that kind are expected to follow. Moreover, PD-L1 testing can provide clinicians with valuable information even if the test is not mandatory (i. e., complementary diagnostics). PD-L1 staining requires a highly specific staining over a broad dynamic range. Sensitive and specific primary antibodies and suitable staining protocols are prerequisite. Selection of appropriate patients' materials, validation and contiguous quality assurance need to meet the highest standards. There are different scoring algorithms for PD-L1 stainings which are specific to tumor entities and certain clinical decisions. The tumor proportion score (TPS) is a PD-L1 measurement which is applied, for example, to lung cancer, head and neck cancer and melanomas. Within this approach, only membranous staining of tumor cells is regarded as a significant staining. In contrast, the combined positivity score (CPS) and inflammatory cell (IC) scoring include or are restricted to PD-L1 expression in certain inflammatory cells, respectively. CPS and IC scoring are standard measurements of PD-L1 in urothelial carcinoma.

[Epithelioid, biphasic and mixed tumors of soft tissue]

Epithelioid soft tissue tumors consist exclusively of epithelioid tumor cells. Biphasic tumors are composed of both a spindle-cell and an epithelioid component. The rare mixed tumors of soft tissue show a broader variety of cellular and stromal differentiation but also include at least one, possibly several, epithelioid portions.The close morphological similarity of some of these entities with each other, as well as with the more frequent soft tissue metastases of carcinomas, carcinosarcomas, and melanomas, to malignant mesothelioma and certain lymphomas, can often make the correct diagnosis extremely difficult. Recent advances in the detection of certain molecular alterations (mostly chromosomal translocations) have contributed to changes in tumor classification but also to improved pathological diagnostics (e.g. through the development of potent diagnostic antibodies) and biological understanding.The present overview should help the pathologist in the diagnosis of these rare tumors through the classical approach of morphological pattern recognition. The most important entities are discussed and illustrated in more detail, with the incorporation of the latest immunohistochemical and molecular aspects and the differential diagnosis of similar tumors.

[Systemic therapy of sarcomas : New biomarkers and therapeutic strategies]

Diagnostics and treatment of mesenchymal tumors (i.e. soft tissue sarcomas, gastrointestinal stromal tumors, and bone sarcomas) have changed dramatically in the past few years. Molecular and immunohistochemical biomarkers contribute significantly to improved diagnostics. They also play an increasing role in terms of clinical treatment decisions.Grading and tumor type-specific outcome data provide the basis for adjuvant chemotherapy of localized sarcomas. Recurrent gene fusions become more important as predictive biomarkers for targeted therapies in the context of systemic treatments. Immuno-oncology-based approaches are currently being studied in clinical trials, and the first responses of selected patients have been demonstrated. However, the role of predictive biomarkers in this field, such as PD-L1, still needs to be elucidated. Comprehensive genetic analyses of metastatic sarcomas will continue to identify additional therapeutic targets and the corresponding biomarkers.

[Round-cell sarcomas]

Round-cell sarcomas represent highly malignant tumors that occur predominantly in children, adolescents, and young adults. Round-cell sarcomas are caused by recurrent translocations that involve certain transcription factors. Ewing's sarcoma, Ewing-like sarcomas (e.g. CIC-DUX positive or BCOR positive sarcomas), desmoplastic small round-cell tumors (DSRCTs), and alveolar rhabdomyosarcomas (ARMs) are typical examples of this particular group of sarcomas. These entities differ in their tumor genetics, which is correlated with immunohistochemical expression profiles and with clinical phenotypes. Classification should be based on molecular findings. Immunohistochemistry may serve as a surrogate marker.

Abstract P4-02-08: Statistical modeling of influential variables affecting HER2-positivity in breast cancer: Final analyses from two large, multicenter, noninterventional studies in Germany

Background:

While HER2 testing in breast cancer (BC) has been routine for over a decade, testing quality remains a challenge. Currently, HER2-positivity rate is the only recommended quality indicator. However, the large, observational, prospective NIU HER2 study in Germany quantified the impact of patient- and tumor-related characteristics such as histologic grade, hormone receptor (HR) status, histologic subtype, age, and nodal status on HER2-positivity, indicating that these factors need to be considered when evaluating HER2-positivity as a measure of testing quality (Rüschoff et al. Mod Pathol 2017). We now report the final analyses from the multicenter EPI HER2 BC study (ML29763, NCT02666261) in Germany where we compared NIU and EPI study data, and aimed to validate the NIU study model.

Methods:

Data from eligible patients with invasive BC were collected (HER2 test result; patient- and tumor-related factors) and variables influencing HER2-positivity identified and compared between studies. The NIU study model was validated and its predictive power determined using newly collected data from the EPI study, with cutoff and variable coefficients from the previous NIU analysis. Additional promising variables were explored, and their relative influence investigated, using multiple stepwise logistic regression.

Results:

In total, 14,729 (EPI) and 15,281 (NIU) BC samples were analyzed. Distributions of the main variables were comparable; overall HER2-positivity rates were 13.47% (EPI) and 14.24% (NIU). Fitting the NIU study model to EPI study data demonstrated that all five covariates from the NIU study analyses significantly affected HER2-positivity (p &lt; 0.01); the influence for each covariate differed only slightly between studies (in EPI, histologic grade had most influence followed by histologic subtype, HR status, nodal status, and age). Prediction profiles were used to visualize the relationship between the model-predicted probability of HER2-positivity and the five identified covariates, which showed good comparability between studies. The receiver operating characteristics area under the curve (ROC AUC) of the NIU model used to predict HER2-positivity in the EPI study data was close to that of the model fitted to the NIU data, thus successfully validating the NIU model. To further improve the model, the categorical HR status was replaced by estrogen receptor (ER) and progesterone receptor (PgR) expression. Inclusion of ER and PgR as continuous variables improved the predictive strength of the model (ROC AUC = 0.74; sensitivity = 0.76; specificity = 0.63). Based on this improved model, PgR status had the highest influence on HER2-positivity, followed by histologic grade, histologic subtype, nodal status, ER status, and age.

Conclusions:

Results from our analyses confirm the statistically and clinically significant influence of patient- and tumor-related factors on HER2-positivity, and highlight the necessity to integrate these factors into the quality control assessment of HER2 testing. Implementation of this model in routine practice may assist in addressing issues with interlaboratory variation, and help to identify centers with HER2 testing problems more accurately.

Citation Format: Rüschoff J, Lebeau A, Kreipe H, Sinn P, Schildhaus H-U, Decker T, Ammann J, Künzel C, Koch W, Untch M. Statistical modeling of influential variables affecting HER2-positivity in breast cancer: Final analyses from two large, multicenter, noninterventional studies in Germany [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-02-08.

Abstract P6-03-01: Variables influencing HER2-positivity in breast cancer: Assessment and validation of a statistical model based on two multicenter noninterventional studies in Germany

Background:

HER2 testing in breast cancer (BC), routine for &gt;10 years, allows selection of patients (pts) for HER2-targeted therapy; however, testing quality remains a concern. While guidelines recommend assessment of HER2-positivity rates as a quality indicator, the influence of patient- or tumor-related factors on variability was unknown until we identified the effect (in order of influence) of histologic grade, hormone receptor (HR) status, histologic subtype, age, and nodal status in a large, multicenter, observational study in Germany (NIU HER2 study; Rüschoff et al., Mod Pathol 2017). Based on these variables and the statistical model developed, potential issues with HER2 testing quality in local practice may be identified. We now report interim analyses from a multicenter study in Germany (EPI HER2 BC study; NCT02666261), where data from the NIU and EPI studies were compared and the validity of the NIU study model assessed.

Methods:

Routine HER2 test results and patient- and tumor-related data were collected from eligible pts with BC. Factors influencing HER2-positivity rates in the EPI study were compared with those identified in the NIU study. The predictive power of the NIU study model, fitted to EPI data, was determined and assessments performed using the variable coefficients and cutoff resulting from the NIU study analysis. Attempts were also made to improve the model.

Results:

Analyses included 15281 (NIU) and 6019 (EPI) invasive BC samples. The distribution of relevant variables, including HER2-positivity rate (NIU: 14.4%; EPI: 13.5%), was comparable. When the NIU study model was fitted to EPI study data, all five covariates identified in the NIU analyses had a significant effect on HER2-positivity (p&lt;0.001); the order of influence for covariates differed between studies (EPI [in order of influence]: histologic grading, histologic subtype, HR status, nodal status, and age). The relationship between HER2-positivity rate and the combined influence of covariates, visualized with the NIU study prediction profiler, was reproduced with EPI study data. The NIU study statistical model, with variable coefficients and cut-point determined in the NIU study, was used to predict the HER2-positivity of samples in EPI; if their NIU model-estimated probability of positivity was &gt;0.1407, the resulting sensitivity, specificity, and receiver operating characteristic (ROC) area under the curve (AUC) were 0.7032, 0.6622, and 0.7259, respectively. Thus, initial validation of the NIU study model with EPI data was successful. Semiquantitative estrogen and progesterone receptor expression data were available from EPI only; their inclusion as independent continuous, rather than categorical, variables improved the model (ROC AUC = 0.7533).

Conclusions:

The statistical modeling approach used to analyze data from the NIU study showed that patient- or tumor-related characteristics should be considered when assessing HER2 testing quality. Our present analysis validates and improves upon this statistical model and further highlights the need to assess HER2 testing quality in BC. Comparison of calculated vs actual positivity rates may help identify centers with potential HER2 testing quality issues.

Citation Format: Rüschoff J, Lebeau A, Kreipe H, Gerharz CD, Sinn P, Schildhaus H-U, Tennstedt-Schenk C, Ammann JU, Künzel C, Koch W, Untch M. Variables influencing HER2-positivity in breast cancer: Assessment and validation of a statistical model based on two multicenter noninterventional studies in Germany [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-03-01.

[Sarcoma of the spleen with MDM2 expression]

Primary sarcomas and sarcoma metastases are a rarity in the spleen. We report on the case of a 69-year-old male patient presenting with unclear abdominal symptoms and computed tomography (CT) revealed a tumor mass in the spleen. Histologically the tumor mass predominantly showed features of a spindle cell sarcoma with lymphoid infiltrates. The expression and amplification of MDM2 could be demonstrated by means of immunohistochemistry and fluorescence in situ hybridization (FISH). Furthermore, staging examinations did not reveal indications of any other primary tumors. These preliminary findings were suggestive of a dedifferentiated liposarcoma; however, in the further diagnostic work-up the tumor showed strong expression of CD21 and CD23 and was ultimately diagnosed as a follicular dendritic cell sarcoma (FDCS). The case emphasizes that MDM2 expression represents a possible pitfall in the diagnosis of spindle cell tumors. The differential diagnostic distinction between FDCS and a dedifferentiated liposarcoma is discussed.

Pelvic lymph node dissection for nodal oligometastatic prostate cancer detected by 68Ga-PSMA-positron emission tomography/computerized tomography

BACKGROUND

The first evaluation of pelvic extended lymph node dissection (pLND) in oligometastatic prostate cancer (PCa) detected by (68)Ga-PSMA PET/CT.

METHODS

Retrospective analysis of 35 PCa patients underwent (68)Ga-PSMA PET/CT affected by biochemical recurrence (BCR) after curative treatment (n = 23) or before primary therapy of high-risk PCa (n = 12). We performed pLND associated with pathologic imaging in 17 men with nodal oligometastatic PCa.

RESULTS

Indicative lesions for PCa in PET/CT were detected in 91.4% (32 of 35) of patients. Nodal, bone, visceral (pulmonary), and within the prostate suspected disease were detected in 72% (23 of 32), 16% (5 of 32), 6% (2 of 32), and 47% (15 of 32) of patients, respectively. Median serum PSA in patients with pathological radiotracer uptake in recurrent and high-risk PCa patients was 2.9 ng/ml (range 0.18-30) and 19.5 ng/ml (range 6-90), respectively. The median number of removed lymph nodes with pLND in recurrent and high-risk PCa was 10 (range 4-17) and 12 (range 8-29) per patient and the median number of positive lymph nodes was 1 (range 1-2) and 3 (2-3) per patient, respectively. In total, two false positive and one false-negative lymph node were found. Diagnostic accuracies per nodal lesion in total of 213 removed nodes: sensitivity, 94%; specificity, 99%; positive predictive value (PPV), 89%, and negative predictive value (NPV), 99.5%. After pLND, 53% (9 of 17) of patients received androgen deprivation therapy and/or radiation therapy and hormonal therapy, while 47% (8 of 17) of patients remained free of any post-surgery therapy. Follow-up PSA remained less than 0.2 ng/ml in 82% (14 of 17) of patients. After pLND, immediate BCR (PSA never measured less than 0.2 ng/ml) in 18% (3 of 17) of patients was recorded.

CONCLUSIONS

This represents the first study of pLND in the setting of nodal oligometastatic PCa detected by (68)Ga-PSMA PET/CT. The use of (68)Ga-PSMA PET/CT could be to improve the accuracy for the detection of nodal micrometastases. These promising findings need validation in larger studies.

[Molecular pathology of soft tissue tumors: Contribution to diagnosis and therapy prediction]

Soft tissue tumors are often challenging for pathologists on the basis of morphology alone; therefore, tumor-specific chromosomal aberrations, such as translocations and fusions, amplifications or deletions can be diagnostically useful. Fluorescence in situ hybridization is widely used for the detection of most aberrations in routine diagnostics. Furthermore, reverse transcriptase PCR, sequencing and specific immunohistochemical assays are also applied. Next generation sequencing has already contributed to the identification of hitherto unknown aberrations. Molecular pathology is mainly used in sarcomas to discriminate between different tumor entities. In terms of personalized therapy and targeted treatment, molecular pathology can be utilized to detect predictive markers.

Complete metabolic response in a patient with repeatedly relapsed non-small cell lung cancer harboring ROS1 gene rearrangement after treatment with crizotinib

A 55-year-old Caucasian woman with lung adenocarcinoma stage IV presented with repeated relapse after treatment with cytotoxic chemotherapy (carboplatin, gemcitabine, docetaxel, pemetrexed) and targeted agents (erlotinib, cetuximab, sunitinib). Comprehensive molecular diagnostics (EGFR-, ALK-, RAS-, BRAF-, PIK3CA-, HER2- and DDR2-aberrations) were performed and failed initially to detect any driver mutation. While the patient suffered from rapid deterioration of her general condition, in particular from progressive dyspnea due to lung metastases, we implemented screening for RET- and ROS1 translocations into our molecular diagnostic program based on recent reports of these new molecular subgroups in lung adenocarcinoma. On retesting the patient's tumor sample was found to harbor a ROS1-translocation. The patient was subsequently treated with crizotinib and experienced a pronounced clinical improvement corresponding to a complete metabolic response in (18)F-FDG-PET and a good and confirmed partial response in CT (RECIST 1.1). Our case exemplifies the need for rapid implementation of newly discovered rare genetic lung cancer subtypes in routine molecular diagnostics.

Postradiation cutaneous angiosarcoma after treatment of breast carcinoma is characterized by MYC amplification in contrast to atypical vascular lesions after radiotherapy and control cases: clinicopathological, immunohistochemical and molecular analysis of 66 cases

Postradiation cutaneous vascular lesions after treatment of breast carcinoma comprise a heterogeneous group of benign, atypical, and malignant lesions and are best regarded as points along a morphological spectrum. We analyzed a series of cutaneous angiosarcomas after treatment of breast cancer in comparison with control cases and cases of atypical vascular lesions with special emphasis on the expression and amplification of MYC. The 66 cases were divided into control cases (5), cases in which a slight vascular proliferation was seen after radiotherapy of breast cancer (12), cases of atypical vascular lesions after radiotherapy (16), cases of postradiation cutaneous angiosarcomas (25), and cases of angiosarcomas of skin and soft tissues unrelated to radiotherapy (8). None of the control cases (2 M, 3 F, 20-76 years), of cases showing slight vascular proliferation, dermal fibrosis and inflammation after radiotherapy of breast cancer (12 F, 48-79 years), of cases of atypical vascular lesions after radiotherapy (16 F, 29-81 years), and of cases of angiosarcomas of skin and soft tissues unrelated to radiotherapy (3 M, 5 F, 25-92 years) showed an amplification of MYC by FISH analysis. In striking contrast, in all cases of postradiation cutaneous angiosarcomas (25 F, 46-95 years), MYC amplification was found by FISH analysis in a variable number of counted nuclei. Immunohistochemically, strong positive nuclear staining for MYC and prox-1 was seen in cases of postradiation cutaneous angiosarcoma, whereas control cases and cases of atypical vascular proliferation after radiotherapy were negative for MYC, and stained only focally positive for prox-1 in a number of cases. In conclusion, the presence of MYC amplification represents an important additional diagnostic tool in the distinction of postradiation cutaneous angiosarcomas from atypical vascular lesions after radiotherapy. Immunohistochemical stainings for MYC are useful for mapping of these lesions and for careful tumor margin control.

[Are sarcoma centers needed in Germany? Experience gained with the 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.

[Gastrointestinal stromal tumors of the stomach. Updates and differences compared to other locations]

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]

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.

[Pathology and molecular biology of gastrointestinal stromal tumors (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.

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.

[Malignant mixed Müllerian tumor of the urinary bladder]

True mixed epithelial-mesenchymal tumors of the urinary bladder are exceedingly rare, and only two vesical adenosarcomas have been reported to date. These tumors originated from bladder endometriosis, and malignant transformation of endometriosis has been described, with endometrioid and clear-cell carcinomas being the most common malignancies. We report an unusual case of a malignant mixed Müllerian tumor with heterologous rhabdomyoblastic differentiation, which originated in the urinary bladder of a postmenopausal woman. To the best of our knowledge, such a neoplasm has not yet been reported in the literature.

Extraosseous osteosarcoma arising from the small intestinal mesentery

Extraskeletal osteosarcoma (EOS) is a highly aggressive and exceedingly rare mesenchymal tumor. Due to the rare nature of the disease, the diagnosis can be difficult and is often confirmed only after diagnostic laparotomy and histopathology. We describe the clinical history, radiologic and histomorphologic presentation, and clinical management of a 61-year-old patient who presented with abdominal pain. Abdominal ultrasound and computerized tomography (CT) scan revealed a calcified intra-abdominal mass. Following an explorative laparotomy, histology showed a large extraosseous osteosarcoma of the small bowel mesentery. Therapy according to the Cooperative Sarcoma Study-96 (COSS-96) was commenced. Diagnosis, management, and outcome in the context of the current literature are discussed. To our knowledge, this is the first description of an extraosseous osteosarcomas in the small bowel mesentery in the literature.

[Activating mutations in receptor tyrosine kinases with relevance for treatment of gastrointestinal stromal tumors]

AIMS

Receptor tyrosine kinases have been shown to be a challenging target for the treatment of hematologic diseases and solid tumors. One very effective tyrosine kinase inhibitor is imatinib mesylate inhibiting the KIT receptor tyrosine kinase in gastrointestinal stromal tumors (GISTs) which often carry activating mutations in the KIT gene. Our own observations show that the location of the underlying mutations influence the response to treatment with imatinib.

METHODS

In Bonn, nearly 1000 GISTs have been characterized molecularily before and/or under treatment with tyrosine kinase inhibitors. Tumor-DNA was extracted from paraffine-embedded material, amplified in all known hot spots of KIT (exons 9, 11, 13, 14, 17) and PDGFRcx (exons 12, 14, 18) and sequenced directly.

RESULTS

The best response to treatment with imatinib is achieved in GISTs with an underlying KIT mutation in exon 11 encoding the juxtamembranous domain. Exon 9 mutated GISTs respond in only half of the cases. GISTs with mutations in the tyrosine kinase domain 1 or 2 are very rare (less than 1%) and are thought to be resistant. PDGFRalpha-mutated GISTs are resistant when carrying the most common point mutation D842V (exon 18) and may respond when deletions occur in exon 18. Low response rates are achieved in tumors without detectable mutation. Under treatment, secondary KIT mutations may occur leading to resistance to treatment.

CONCLUSIONS

The molecular status of GISTs plays a central role for treatment response. Its evaluation will be mandatory in the future at least in tumors with intermediate or high risk criteria.

[Therapeutic targets in gastrointestinal stromal tumors]

Gastrointestinal stromal tumors (GISTs), the most common mesenchymal tumors in the gastrointestinal tract, metastasize in up to 50 % of cases and are resistant to conventional radio- and chemotherapy. They are characterized by the expression of the type III receptor tyrosine kinase KIT which is the most important diagnostic immunohistochemical feature. Genomically, the majority of GISTs carry heterozygous mutations in the KIT or the PDGF receptor alpha gene leading to an autophosphorylation of the respective receptor protein. The evaluation of the mutational status allows the subdivision of GISTs into different prognostic sub-groups. For example, GISTs carrying an activating mutation in PDGF receptor alpha are most often located in the stomach and seem to have a better prognosis than GISTs with a KIT mutation. Specific mutational subtypes of KIT mutations in exon 11 (esp. proximal deletions of codons tryptophane-557 and lysine-558) have a significantly higher metastatic risk than GISTs with KIT mutations located in the distal part of exon 11 (esp. insertions/duplications). GISTs in the small bowel most often carry KIT exon 9 mutations and have a worse prognosis than GISTs with exon 11 mutations. Mutational subtype in KIT or PDGF receptor alpha not only influences the biological behavior of GISTs but also their response to treatment with imatinib, a tyrosine kinase inhibitor also inhibiting ARG, PDGF receptor beta and BCR-ABL. KIT exon 11 mutated tumors show response rates of up to 80 % of cases whereas KIT exon 9 mutated GISTs respond in less then 50 %. GISTs without detectable KIT mutation in these both exons often are resistant to imatinib. The development of secondary resistance to imatinib in GIST patients occurs in up to 40% of cases and is partly due to secondary KIT mutations occuring additionally to the primary mutation. Actually, several studies evaluate the efficacy of alternative small molecules such as SU 11248, RAD001 and AMG706 inhibiting signal transduction pathways downstream of KIT and PDGF receptor alpha. In summary, mutational status in KIT or PDGF receptor alpha of GISTs is relevant for prognosis, for response to treatment and for further insights into mechanisms of treatment failure.

[Intramuscular angioma in the hand. A case report]

Intramuscular angiomas are rare vascular tumors with locally aggressive growth between the fibers of muscle. A malignant aspect poses a danger for the function of the hand. We report the case of a 32-year-old woman with a painless tumor in the thenar. Physical examination showed a 2 x 3 x 5 cm fixed and engorged swelling. Perfusion and sensibility were intact. The flexion and opposition of the thumb were reduced. CAT showed a tumor of the thenar with a solid structure with signal enhancement after administration of contrast medium. Histologic examination after local resection showed an intramuscular angioma. Intramuscular angiomas have a malignant aspect because of the rapid and infiltrative growth followed by functional impairment, pain, and deformity. A high rate of recurrence is described. Thus, radical excision is indicated.

A HhaI polymorphism in the human MEP1A gene encoding the alpha subunit of the metalloendopeptidase meprin

Meprins are membrane-bound oligomeric metalloendopeptidases belonging to the astacin protein family. The meprin isolated from human small intestinal mucosa was originally known as N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PABA peptide) hydrolase (PPH). Here we describe the first genetic marker for the human MEP1A gene encoding the alpha subunit of this enzyme. The polymorphism changes codon 176 of the mature alpha chain of PPH from CAA to CAG. Using the polymerase chain reaction, this variation is easily detectable as a HhaI restriction fragment length polymorphism. The two alleles are both common, probably in all major races.

Fine mapping of MEP1A, the gene encoding the alpha subunit of the metalloendopeptidase meprin, to human chromosome 6P21

Meprins are kidney and intestinal proteases encoded by two distinct genes, MEP1A and MEP1B. MEP1A was previously mapped to human chromosome 6p, by the use of radiation and somatic cell hybrids, in the region containing the gene for autosomal recessive polycystic kidney disease (ARPKD). We now report the fine mapping of MEP1A using yeast artificial chromosome clones, and linkage analysis of ARPKD families. The results from both physical and genetic mapping exclude MEP1A as a candidate for ARPKD. These studies place MEP1A in a region more telomeric to 6p12 and closer to the HLA loci than previously reported. More specifically, MEP1A is localized between loci D6S272 and D6S282, close to D6S452, on human chromosome 6p21.2-p21.1. The more precise location of MEP1A will facilitate genetic studies of this locus and clarify the relation of this gene to others.