PCR-based analysis of PD-L1 RNA expression in lung cancer: comparison with commonly used immunohistochemical assays.

BACKGROUND: PD-L1 testing is currently performed by immunohistochemistry (IHC). We questioned whether the results of PCR-based measurement of PD-L1 RNA expression correlate with IHC scores obtained by different commercial assays. MATERIALS AND METHODS: 167 consecutive non-squamous non-small cell lung carcinomas (NSCLCs) were analyzed for PD-L1 RNA expression and 22C3, SP263, and SP142 IHC scoring using recommended cut-offs. RNA expression was divided into low, moderate, and high categories. RESULTS: RNA and protein expression demonstrated moderate correlation as continuous variables. Using prespecified RNA cut-offs, PCR testing showed a high negative predictive value towards the IHC analysis: the share of PD-L1 protein-negative tumors among cases classified as PD-L1-low by the PCR test reached 92-99% for all three antibodies. Meanwhile, about half of cases with moderate to high PD-L1 RNA expression had IHC staining in less than 1% tumor cells as determined by 22C3 or SP263 antibodies. Among the 51 discordant cases, which had <1% tumor staining by both 22C3 and SP263 clones but high RNA level, 29 (57%) showed ≥1% positive immune cells by SP263 and/or 22C3, 14 cases (27%) had detectable IHC expression in 0.1-0.9% tumor or immune cells by SP263 and/or 22C3, and 8 (16%) were entirely negative by IHC. CONCLUSION: Some NSCLCs demonstrate readily detectable PD-L1 expression on the level of RNA, but fall below commonly accepted cut-offs by IHC. It remains to be studied whether these discrepancies are attributed to technical or biological reasons. Clinical sensitivity of these tumors to immune therapy deserves additional investigations.

Gene rearrangements in consecutive series of pediatric inflammatory myofibroblastic tumors.

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.

Nuclear Protein of the Testis Midline Carcinoma Masquerading as a Primary Mediastinal Seminoma.

Nuclear protein of the testis (NUT) midline carcinomas are rare aggressive carcinomas characterized by chromosomal rearrangements that involve the gene encoding the NUT. This article reviews the clinicopathologic features and the differential diagnosis of these malignancies.