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Background and objective Analysis of programmed death ligand‐1 (PD‐L1) in tumour samples is necessary to identify candidates for anti‐PD‐L1/PD‐L1 therapy. Because PD‐L1 is evaluated by immunohistochemistry (IHC), an adequate amount of tumour tissue is a prerequisite for PD‐L1 testing. To examine whether pleural fluid might be an alternative to biopsy/resection specimens for IHC evaluation of PD‐L1 in patients with non‐small cell lung carcinoma (NSCLC), we compared PD‐L1 by IHC between histological specimens and matched pleural fluid. Methods A retrospective cohort study of patients with NSCLC who underwent core biopsy of a lung mass/surgical resection with PD‐L1 IHC and had a pleural fluid cell block (CB) available for PD‐L1 staining was conducted. PD‐L1 was categorized as negative (PD‐L1 in <1% of tumour cells), moderately positive (PD‐L1 in ≥1% to <50%), strongly positive (PD‐L1 ≥ 50) or inadequate for PD‐L1 testing (<100 tumour cells in the CB). Weighted Cohen's kappa was calculated to evaluate the agreement between PD‐L1 on biopsy/resection specimen and pleural fluid for variables with more than two categories. Results Of the 115 patients included in this study, 82 (71.3%) had at least 100 tumour cells and were included in the analysis. Of these, 80 (97.6%) had adenocarcinoma. For PD‐L1 of histological specimens versus pleural fluid categorized as negative, moderately positive or strongly positive, the weighted kappa statistic was 0.76 (95% CI: 0.64–0.88), and the concordance was 0.78 (95% CI: 0.68–0.86). Conclusion Correlation and concordance are high between PD‐L1 in histological specimens and matched pleural fluid. Evaluation of PD‐L1 in pleural fluid should be considered in patients unable to undergo histological biopsies.

Objective: Interest in immune therapies has exploded since the 2014 approval of first-generation programmed cell death 1 blocking antibodies for use in advanced melanoma. Clinical trials have focused primarily on histological material as the gold standard for evaluating programmed death ligand 1 (PD-L1) by immunoperoxidase (IPOX) studies. Studies validating the use of cytological specimens in the assessment of PD-L1 by IPOX staining are needed to optimise tissue utilisation in complementary diagnostic testing.Methods: Twenty-three melanoma surgical biopsies (SBx) with an IPOX stain for PD-L1 clone 28-8, and a corresponding cytological specimen from the same patient, adequate for PD-L1 evaluation, were selected. Cell-transfer cell blocks (CBs) andconventional CBs were used to perform PD-L1 testing. Tumour proportion scores (TPS) were generated and the results were correlated with the corresponding SBx.Results: Overall agreement (OA) using a ≥1% TPS cut-off for SBx compared to CB was 88.9%, positive percent agreement (PPA) was 87.5%, and negative percent agreement (NPA) was 100%, OA using a ≥5% TPS cut-off was 55.6%, PPA was 42.9%, and NPA was 100%. SBx compared to cell-transfer CB using a ≥1% TPS cutoff had an OA of 65.2%, a PPA of 55.6%, and a NPA of 100%, while a ≥5% TPS cut-off generated an OA of 52.2%, a PPA of 35.7%, and a NPA of 77.8%.Conclusion: Our results demonstrate that cytological material, particularly conventional CB, is a viable alternative for evaluating PD-L1 in melanoma cases and suggest that a lower threshold (≥1%) may be beneficial when evaluating cytological material. K E Y W O R D Scell block, cytopathology, immunocytochemistry, immunohistochemistry, melanoma, programmed death ligand 1

We describe a rapid and efficient 5-step program of defined factors for the genesis of brain myelin-forming oligodendrocytes (OLs) from embryonic stem cells (ESCs). The OLs emerge on the same time frame in vitro as seen in vivo. Factors promoting neural induction (retinoids, noggin) are required, while exogenous Sonic hedgehog is not. In contrast we were unable to generate OLs by trans-differentiation of ethically neutral mesenchymal stem cells, indicating a requirement for cis-differentiation via neural ectoderm for OL genesis. In the ESC-derived cultures, our optimized protocol generated a mixed population with 49% O4(+), Olig2(+) OL lineage cells. These cultures also retained pluripotential markers including Oct4, and an analysis of embryoid body formation in vitro, and allogeneic grafts in vivo, revealed that the ESC-derived cultures also retained teratogenic cells. The frequency of embryoid body formation from terminal differentiated OL cultures was 0.001%, 100-fold lower than that from ESCs. Our results provide the first quantitative measurement of teratogenicity in ESC-derived, exhaustively differentiated allogeneic grafts, and demonstrate the unequivocal need to purify ESC-derived cells in order to generate a safe population for regenerative therapy.

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The majority of mixed epithelial and stromal tumors (MEST) of the kidney are benign entities found in female patients. Malignant MEST of the kidney is an extremely rare entity that often behaves clinically similar to an undifferentiated sarcoma. We report a case of a malignant MEST with synchronous papillary and clear cell renal cell carcinomas (RCCs) in a 61-year-old Caucasian man who presented with an incidental finding of a left renal mass on workup for back pain. The patient underwent a left radical nephrectomy, with histopathology confirming a malignant MEST, intimately associated papillary RCC, and separate adjacent focus of clear cell RCC.

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Objectives Persistent antigen exposure leads to the accumulation of lymphocytes and subsequent tertiary lymphoid structures (TLS). We investigated the relationship of tumor microenvironment (TME) with respect to programmed death ligand 1 (PD-L1), its receptor programmed death 1 (PD-1), and TLS in upper tract urothelial carcinoma (UTUC) cases and compared them with UTUC associated with urothelial bladder carcinoma (UTUC-BCa). Methods We retrospectively identified 72 patients with UTUC. Representative slides were reviewed, and TLS were counted. Immunohistochemical stains for PD-1 and PD-L1 were performed. PD-1–positive lymphocytes were counted and H-score for PD-L1–positive membranous staining was determined. Results PD-L1 expression in the tumor was present in 55.1% of the UTUC cases. Higher stage was associated with increased PD-L1 expression (P = .035). TLS were present in 33.3% and their presence was significantly associated with PD-L1 positivity (P = .024). This association remained significant after adjustment for UTUC-BCa. TLS were also associated with a greater number of infiltrating PD-1-positive lymphocytes (P = .013). Conclusions This study is one of the first comparative studies of the TME in UTUC and UTUC-BCa. PD-L1 is expressed in a subset of UTUC and is associated with TLS. The presence of TLS is an inherent characteristic of UTUC and not secondary to the presence of BCa.