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Thomas Keller

Zimmer Biomet (Netherlands)

ORCID: 0000-0001-8160-3046

Publishes on Cellular Mechanics and Interactions, Forensic Toxicology and Drug Analysis, Cell Image Analysis Techniques. 239 papers and 5.6k citations.

239Publications
5.6kTotal Citations

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Top publicationsby citations

Conjunctive p16INK4a Testing Significantly Increases Accuracy in Diagnosing High-Grade Cervical Intraepithelial Neoplasia
Christine Bergeron, Jaume Ordï, Dietmar Schmidt et al.|American Journal of Clinical Pathology|2010
Cited by 231

The histopathologic interpretation of cervical intraepithelial neoplasia (CIN) is subject to a high level of interobserver variability and a substantial number of false-positive and false-negative results. We assessed the impact of the conjunctive interpretation of p16(INK4a)-immunostained slides on the accuracy of community-based pathologists in diagnosing high-grade cervical intraepithelial neoplasia (CIN; CIN 2 and CIN 3) in biopsy specimens. Twelve pathologists rendered independent diagnoses on a set of 500 H&E-stained cervical punch and conization specimens. Results were compared with a dichotomized "gold standard" established by consensus of 3 gynecopathology experts. When p16(INK4a)-immunostained slides were added and conjunctively interpreted with the H&E-stained slides, a significant increase in diagnostic accuracy for the detection of high-grade CIN was observed (P = .0004). Sensitivity for high-grade CIN was increased by 13%, cutting the rate of false-negative results in half. Agreement of community-based pathologists in diagnosing high-grade CIN was significantly improved (mean kappa values advanced from 0.566 to 0.749; P < .0001). Reproducibility of p16(INK4a) stain interpretation was excellent (kappa = 0.899). Our results show that conjunctive interpretation of p16(INK4a)-stained slides could significantly improve the routine interpretation of cervical histopathology.

Screening for Cervical Cancer Precursors With p16/Ki-67 Dual-Stained Cytology: Results of the PALMS Study
Hans Ikenberg, Christine Bergeron, Dietmar Schmidt et al.|JNCI Journal of the National Cancer Institute|2013
Cited by 224Open Access

BACKGROUND: Pap cytology is known to be more specific but less sensitive than testing for human papillomavirus (HPV) for the detection of high-grade cervical intraepithelial neoplasia (CIN2+). We assessed whether p16/Ki-67 dual-stained cytology, a biomarker combination indicative of transforming HPV infections, can provide high sensitivity for CIN2+ in screening while maintaining high specificity. Results were compared with Pap cytology and HPV testing. METHODS: A total of 27,349 women 18 years or older attending routine cervical cancer screening were prospectively enrolled in five European countries. Pap cytology, p16/Ki-67 immunostaining, and HPV testing were performed on all women. Positive test results triggered colposcopy referral, except for women younger than 30 years with only positive HPV test results. Presence of CIN2+ on adjudicated histology was used as the reference standard. Two-sided bias-corrected McNemar P values were determined. RESULTS: The p16/Ki-67 dual-stained cytology positivity rates were comparable with the prevalence of abnormal Pap cytology results and less than 50% of the positivity rates observed for HPV testing. In women of all ages, dual-stained cytology was more sensitive than Pap cytology (86.7% vs 68.5%; P < .001) for detecting CIN2+, with comparable specificity (95.2% vs 95.4%; P = .15). The relative performance of the tests was similar in both groups of women: younger than age 30 and 30 years or older. HPV testing in women 30 years or older was more sensitive than dual-stained cytology (93.3% vs 84.7%; P = .03) but less specific (93.0% vs 96.2%; P < .001). CONCLUSIONS: The p16/Ki-67 dual-stained cytology combines superior sensitivity and noninferior specificity over Pap cytology for detecting CIN2+. It suggests a potential role of dual-stained cytology in screening, especially in younger women where HPV testing has its limitations.

Lipoxygenase mediates invasion of intrametastatic lymphatic vessels and propagates lymph node metastasis of human mammary carcinoma xenografts in mouse
Dontscho Kerjaschki, Zsuzsanna Bagó-Horváth, Margaretha Rudas et al.|Journal of Clinical Investigation|2011
Cited by 191Open Access

In individuals with mammary carcinoma, the most relevant prognostic predictor of distant organ metastasis and clinical outcome is the status of axillary lymph node metastasis. Metastases form initially in axillary sentinel lymph nodes and progress via connecting lymphatic vessels into postsentinel lymph nodes. However, the mechanisms of consecutive lymph node colonization are unknown. Through the analysis of human mammary carcinomas and their matching axillary lymph nodes, we show here that intrametastatic lymphatic vessels and bulk tumor cell invasion into these vessels highly correlate with formation of postsentinel metastasis. In an in vitro model of tumor bulk invasion, human mammary carcinoma cells caused circular defects in lymphatic endothelial monolayers. These circular defects were highly reminiscent of defects of the lymphovascular walls at sites of tumor invasion in vivo and were primarily generated by the tumor-derived arachidonic acid metabolite 12S-HETE following 15-lipoxygenase-1 (ALOX15) catalysis. Accordingly, pharmacological inhibition and shRNA knockdown of ALOX15 each repressed formation of circular defects in vitro. Importantly, ALOX15 knockdown antagonized formation of lymph node metastasis in xenografted tumors. Furthermore, expression of lipoxygenase in human sentinel lymph node metastases correlated inversely with metastasis-free survival. These results provide evidence that lipoxygenase serves as a mediator of tumor cell invasion into lymphatic vessels and formation of lymph node metastasis in ductal mammary carcinomas.

TEP versus TAPP: comparison of the perioperative outcome in 17,587 patients with a primary unilateral inguinal hernia
F. Köckerling, R. Bittner, Dietmar Jacob et al.|Surgical Endoscopy|2015
Cited by 182Open Access

INTRODUCTION: More than 20 years since the introduction of TAPP and TEP into clinical routine, there is a lack of clarity due to conflicting comparative data. Therefore, more results from registries are needed. PATIENTS AND METHODS: A total of 17,587 patients were enrolled prospectively between September 1, 2009, and April 15, 2013, in the Herniamed registry. Of these patients, 10,887 (61.9%) had a TAPP and 6700 (38.1%) a TEP repair. The dependent variables were intra- and postoperative complication rates, number of reoperations as well as absolute and relative frequencies. The results of unadjusted analyses were verified via multivariable analyses. RESULTS: Multivariable analysis verified the results of unadjusted analysis, indicating that the surgical technique did not have any significant impact, also while taking account of other factors, on occurrence of intraoperative [p = 0.1648; OR = 1.214 (0.923; 1.596)] and general postoperative complications [p = 0.0738; OR = 1.315 (0.974; 1.775)]. Postoperative surgical complications [OR = 2.323 (1.882; 2.866); p < 0.0001] were noted more often after TAPP. Furthermore, the hernia defect size [p < 0.0001; I vs III: OR = 0.439 (0.313; 0.615), II vs III: OR = 0.712 (0.582; 0.872)] or scrotal [p < 0.0001; OR = 2.170 (1.501; 3.137)] hernia and age [p = 0.0002; 10-year OR = 1.135 (1.062; 1.213)] had a significant impact on the occurrence of postoperative complications. Complications were observed more commonly for larger hernia defects and a scrotal hernia. However, the difference in the postoperative complication rate between TEP and TAPP did not result in any difference in the reoperation rate (TEP 0.82% vs TAPP 0.90%; p = 0.6165). CONCLUSION: The intraoperative and general postoperative complication rates as well as the reoperation rate for complications show no significant difference between TEP and TAPP. The higher postoperative complication rate for TAPP, which could be managed conservatively, is partly explained by larger defect sizes, more scrotal hernias and older age.

Ethyl Glucuronide: An Unusual Ethanol Metabolite in Humans. Synthesis, Analytical Data, and Determination in Serum and Urine
Georg Schmitt, Rolf Aderjan, Thomas Keller et al.|Journal of Analytical Toxicology|1995
Cited by 179

Ethyl glucuronide (ethyl beta-D-6-glucosiduronic acid), a minor ethanol metabolite in serum or urine, was determined by gas chromatography-mass spectrometry. Prior to this, ethyl glucuronide was synthesized by the reaction of acetobromo-glucosiduronic acid with ethanol. For the determination of ethyl glucuronide, serum samples were precipitated with acetone, and urine specimens were analyzed after evaporation to dryness. The residues were derivatized with acetic anhydride. Capillary gas chromatography was used to find a retention index value of 1920 for the triacetyl derivative. The mass spectrum of the acetylated ethyl glucuronide was recorded. The calibration is linear in the range investigated (0.1-150 mg/L), and the detection limit is 0.1 mg/L. In individual specimens containing between 0.1 and 4 g ethanol per liter serum, ethyl glucuronide could be detected at concentrations between 3 and 14 mg/L and in the corresponding urine specimens at concentrations between 3 and 130 mg/L.