We developed a high-throughput deep sequencing approach for concomitant MSI and mutational analyses in FFPE specimens. We provided novel insights into clinically relevant alterations in MSI CRC and a rationale for targeting ERBB2/HER2 mutations in Lynch and Lynch-like CRC.

Salivary gland carcinomas (SGCs) are rare and can be subdivided into distinct entities, some of which confer a poor prognosis. As targets for effective systemic therapy are warranted, some studies investigated the role of immune-checkpoint proteins PD-L1 and CTLA-4 in SGC. Our study depicts the expression of lymphocyte activation gene 3 ( LAG3) in a test cohort and a larger validation cohort, totaling 139 SGCs. LAG3 is expressed on tumor-infiltrating lymphocytes (TILs), mediates T cell exhaustion and is subject to numerous currently recruiting clinical studies. Overall, one-third of SGCs were infiltrated by LAG3-expressing TILs with a strikingly high concordance between the test cohort and the validation cohort (30% and 28.2%, respectively). In the validation cohort, entity-wise LAG3 expression frequencies were highly variable. The highest rates were observed in salivary duct carcinoma (SDC; 66.7%) and adenocarcinoma not otherwise specified (ANOS; 50.0%). We observed LAG3 expression on effector T cells and in smaller frequencies also on FOXP3− T helper cells and FOXP3+ Tregs. LAG3 expression significantly correlated with advanced nodal metastases, cytotoxic T cell infiltrate and TP53 mutations. In the group of adenoid cystic carcinomas, LAG3 expression was also associated with a shorter event-free survival (EFS). Tumors with TP53 nonsense mutations ( TP53 null type) exhibited higher LAG3 frequencies and a shorter EFS compared to TP53 wild type. This is the first report of LAG3 expression in SGC, a promising target for immunotherapy. LAG3 blockage could be distinctly applicable for SDC and ANOS, two SGC types with a particularly poor outcome. Electronic supplementary material The online version of this article (10.1007/s00262-020-02551-6) contains supplementary material, which is available to authorized users.

CME Accreditation Statement: This activity ("JMD 2019 CME Program in Molecular Diagnostics") has been planned and implemented in accordance with the accreditation requirements and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint providership of the American Society for Clinical Pathology (ASCP) and the American Society for Investigative Pathology (ASIP). ASCP is accredited by the ACCME to provide continuing medical education for physicians. The ASCP designates this journal-based CME activity ("JMD 2019 CME Program in Molecular Diagnostics") for a maximum of 18.0 AMA PRA Category 1 Credit(s) ä. Physicians should claim only credit commensurate with the extent of their participation in the activity.

Objective:Rare disease Background:Pseudolymphoma is a rare disorder that can mimic lymphoma both clinically and histologically. It usually affects middle-aged females. Since pseudolymphoma is a rare disorder not only is diagnosing the condition difficult, but there is also a lack of standardized treatment guidelines. In the literature, anti-CD20 monoclonal antibody rituximab is described as an effective treatment option. Case Report:46-year-old female fell ill suddenly with swelling and enlargement of her chin. Multiple skin biopsies were done, which were re-evaluated multiple times as well. Each ended with a new diagnosis for the patient. Finally, in the last revision of biopsy material, pseudolymphoma was confirmed. The patient received multiple courses of corticosteroid treatments -locally and systemically -without long lasting effect. After diagnosis of pseudolymphoma, the patient was started on intravenous rituximab and this treatment was effective. Conclusions:Cutaneous pseudolymphoma is a diagnostic challenge. Rituximab is a treatment option for refractory pseudolymphoma. Since there are no treatment guidelines for pseudolymphoma, more clinical studies are needed to establish best treatment options for these patients. Therefore, each reported clinical case is important.

9041 Background: Resistance to early generation epidermal growth factor receptor ( EGFR) tyrosine kinase inhibitors (TKI) inevitably develops in EGFR-mutant lung cancer. The secondary EGFR p.T790M mutation is the driving factor in 60% of cases and 3rd generation EGFR TKIs have been developed to overcome T790M-mediated resistance. However, besides T790M other genetic aberrations such as amplifications of MET may contribute to resistance to EGFR inhibition in the same patient. We here report on the systematic analysis of co-occurring genetic aberrations that may influence response to 3rd generation EGFR TKIs. Methods: Thirty-six patients were treated with 3rd generation EGFR TKIs in the setting of acquired resistance to EGFR inhibition in cancer centers in Germany and Switzerland. Pre-treatment samples were analyzed for co-occurring genetic aberrations in a subset of resistance-related genes including MET, HER2, RAS-gene family, PIK3CA, CTNNB1 and PTEN using next-generation sequencing and fluorescence in-situ hybridization assays. We investigated the association between clinical, epidemiological and molecular data and response to treatment (RECIST 1.1). Results: Co-occurring genetic aberrations were found in 68% of the pre-treatment samples where both, analyses by sequencing and FISH were feasible (N = 25). Efficacy of 3rd generation EGFR TKIs significantly dropped in the presence of high-level MET amplification as compared to wild-type MET (ORR, 0.0%; 95% CI, 0.0-60.4 vs. 70.0%; 95% CI, 45.7-87.2; p = 0.02; median PFS, 1.0 month; 95% CI, 0.37-1.72 months vs. 8.2 months; 95% CI, 1.69-14.77 months; p ≤ 0.001). No statistically significant association was found between treatment efficacy and the molecular status of the genes analyzed or the number of prior EGFR TKIs. Conclusions: Prevalence of additional genetic aberrations is frequent in the setting of acquired resistance to early generation EGFR TKIs and may not necessarily mediate resistance to 3rd generation EGFR TKIs. However, in our analysis high-level amplification of MET was associated with primary treatment failure and might be the main factor underlying resistance in this setting.