Ewing's sarcoma (ES)/peripheral neuroectodermal tumor (PNET) are malignant neoplasms affecting children and young adults. We performed a study to typify the histological diversity and evaluate antibodies that may offer diagnostic/prognostic support. In total, 415 cases of genetically confirmed paraffin-embedded ES/PNET were analyzed on whole sections and in tissue microarrays. This study confirms the structural heterogeneity of ES/PNET, distinguishing three major subtypes: conventional ES (280 cases); PNET (53 cases); and atypical ES/PNET (80), including large cells, vascular-like patterns, spindle pattern, and adamantinoma-like configuration. All cases presented positivity for at least three of the four tested antibodies (CD99, FLI1, HNK1, and CAV1). CAV1 appeared as a diagnostic immunomarker of ES/PNET being positive in CD99-negative cases. Hence, the immunohistochemical analysis confirmed the diagnostic value of all four antibodies, which together cover more than 99% of the tumors, independently of the histological variety. The univariate analysis for survival revealed atypical ES as the only histological parameter apparently associated with less favorable clinical outcome, particularly in the subgroup of patients treated with surgery. In conclusion, the diagnosis of atypical ES is a challenge for the pathologist and needs support from molecular techniques to perform an optimal differential diagnosis with other small round cell tumors.

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Background Inflammatory myofibroblastic tumors (IMTs) are exceptionally rare neoplasms, which are often driven by rearranged tyrosine kinases. Methods This study considered 33 consecutive patients with IMT (median age, 6.6; age range, 0.6‐15.8 years). RNA and cDNA were successfully obtained in 29 cases. The molecular analysis included sequential tests for 5′/3′‐end unbalanced gene expression, variant‐specific PCR, and next‐generation sequencing (NGS). Results 5′/3′‐end unbalanced ALK expression was revealed in 15/29 (52%) IMTs. Strikingly, all these tumors demonstrated high amount of ALK protein detected by immunohistochemistry. Variant‐specific PCR was capable of identifying the type of ALK rearrangement in 11/15 IMTs with 5′/3′‐end unbalanced ALK expression. The remaining four tumors were analyzed by NGS; two known and two novel (CLTC‐ins6del84‐ALK and EEF1G‐ALK) ALK rearrangements were detected. Five IMTs demonstrated 5′/3′‐end unbalanced ROS1 expression, and all these tumors carried TFG‐ROS1 fusion. Nine tumors, which were negative for 5′/3′‐end unbalanced ALK/ROS1 expression, were subjected to further analysis. Variant‐specific PCR revealed two additional tumors with gene rearrangements (TFG‐ROS1 and ETV6‐NTRK3). The remaining seven IMTs were tested by NGS; single instances of TFG‐ROS1 and novel SRF‐PDGFRb translocations were detected. Conclusions Twenty‐four of 29 IMTs (83%) were shown to have druggable rearrangements involving tyrosine kinases, 20 of these 24 gene fusions were detectable by simple and inexpensive PCR assay, which is based on the detection 5′/3′‐end unbalanced gene expression.

the goal of the cLoVeR study was to perform a pairwise comparison of four tests based on the same patient population with non-small cell lung cancer (NSCLC): three validated PDL1 immunohistochemistry (IHC) assays (Ventana SP142, Ventana SP263, Dako 22C3) and one PCR test. Four hundred seventy-three NSCLC samples were obtained from a biobank and were stained using PDL1 IHC assays. Four trained pathologists independently evaluated the percentage of tumor cells (TC) and immune cells (IC) that stained positive at any intensity. PDL1 transcripts were quantified in 437 patients by a standard Taqman RT-PCR assay using SDHA as a reference gene. A concordance analysis was performed to assess (1) the correlation of TC and IC between different assays and (2) the predictive properties of one test for another. "High" RNA expression was detected in 187 of 437 (43%) patients. The percentage of PDL1-positive cells (≥1%) was higher among the IC than the TC in all IHC three assays. The Pearson correlation coefficients (PCC) for TC were 0.71, 0.87, and 0.75 between 22C3/ SP142, 22C3/SP263, and SP263/SP142, respectively. The PCC for IC were 0.45, 0.61, and 0.68 for the same pairs. A low correlation was observed between the PCR test and each of the three IHC assays; however, if a patient tested low/negative by PCR, then they were likely to test negative by any single IHC test with a high probability (92-99%). Among patients who tested positive by PCR, only 9-45% tested positive by IHC assays. There was excellent positive and negative agreement (>91%) between 22C3 and SP263 staining using the recommended individual cutoffs for first-line treatment. PCR RNA expression analysis is not equivalent to IHC. However, this method may have some potential for the identification of PDL1-negative tumors. 22C3 could be considered as a substitute for SP263 in first-line treatment.In recent years, immune checkpoint inhibitors targeting programmed cell death 1 (PD-1) or programmed cell death ligand 1 (PDL1, CD274), have presented an alternative revolutionary therapeutic approach for patients with nonsquamous and squamous non-small-cell lung cancer (NSCLC) 1 .Pembrolizumab, an anti-PD-1 humanized antibody, is recommended as a first-line single agent for patients with metastatic NSCLC and PDL1 expression levels greater than 50% detected by immunohistochemistry (IHC) with the diagnostic antibody 22C3 (Agilent) 2,3 . Pembrolizumab was recently approved for use in the first-line One test-specific cutoff rule for each assay was pre-specified as: for first-line treatment the Tumor Proportion Score (TPS, the percentage of viable tumor cells showing partial or complete membrane staining relative to all viable tumor cells present in the sample) ≥50% for 22C3, TC or IC ≥ 5% for SP142, TC ≥ 25% for SP263, and for second-line treatment TPS ≥ 1% for 22C3, TC ≥ 50% or IC ≥ 10% for SP142, and TC ≥ 25% for SP263 (Table 1). Delta CT = 2 was conditionally chosen as the threshold between "high" ("positive") and "low/absent" ("negative") PDL1 RNA expression. ResultsPatie...

Context.-Echinoderm microtubule-associated proteinlike 4 gene (EML4) and anaplastic lymphoma kinase gene (ALK) fusion was shown to be the driver of tumorigenesis in approximately 3% to 5% of patients with non-small cell lung cancer (NSCLC) and is associated with response to inhibition with crizotinib. However, no complete agreement regarding the best diagnostic test for identification of ALK rearrangements has been achieved yet.Objective.-To investigate the concordance, sensitivity, and specificity of immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and reverse transcription-polymerase chain reaction (RT-PCR) for detection of ALK rearrangements.Design.-Thirty-six prospectively tested patients with NSCLC who had adenocarcinoma and 10 ALK-positive samples were included in the study. All samples were tested by IHC (ALK1 clone, 5A4 clone, D5F3 clone), FISH (LSI ALK Break Apart and ALK FISH Probe), and multiplexed RT-PCR.Results.-Immunohistochemistry staining was successful in all samples. Clone D5F3 showed the best sensitivity and specificity of 100%; clones ALK1 and 5A4 showed sensitivities of 91% with specificity of 100%. Both FISH probes showed concordance with sensitivity and specificity of 100%. Hybridization and RT-PCR were successful in 98% and 93.4% of samples, respectively, with sensitivity of 88% and specificity of 100%. Frequent artifacts leading to misinterpretation were observed with all 3 methodologies.Conclusions.-All 3 methodologies showed good sensitivity, specificity, and concordance, when artifacts were characterized and excluded. However, all ambiguous cases have to be confirmed as ALK rearranged by at least 2 of the 3 methods.