Clinical implications of heterogeneity in PD-L1 immunohistochemical detection in hepatocellular carcinoma: the Blueprint-HCC study.

Programmed cell death ligand-1 immunohistochemical detection (PD-L1 IHC) is a putative predictor of response to PD-1/PD-L1-targeted checkpoint inhibitors. However, there is no gold standard assay in hepatocellular carcinoma (HCC). We evaluated 5 PD-L1 IHC assay platforms (E1LN3, 28-8, 22c3, SP263 and SP142) in 100 HCCs reporting PD-L1 expression in malignant (M) and tumour-infiltrating immune cells (TICs) and non-tumorous cirrhotic tissues (NTICs). We found substantial inter-assay heterogeneity in detecting PD-L1 expression in M (R2 = 0.080-0.921), TICs (Cohen's κ = 0.175-0.396) and NTICs (κ = 0.004-0.505). Such diversity may impact on the reliability and reproducibility of PD-L1 IHC assays as a predictor of response to immune checkpoint inhibitors.

KRAS mutation testing on all non-malignant diagnosis of pancreatic endoscopic ultrasound-guided fine-needle aspiration biopsies improves diagnostic accuracy.

Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is the procedure of choice for the cytologic diagnosis of pancreatic masses. The specificity of EUS-FNA approaches 100%, but the sensitivity is still low, and the high rate of indeterminate (atypical and suspicious) and false-negative results needs improvement. KRAS gene is frequently mutated in pancreatic ductal adenocarcinoma (PDAC) (up to 90%), and mutation analysis of KRAS has been proposed as diagnostic biomarker of PDAC. In most laboratories, KRAS mutation testing is performed by Sanger sequencing or real time-quantitative polymerase chain reaction (RT-qPCR), but these methods may give false-negative results in routine samples, mainly due to low cellularity. In order to increase the sensitivity of EUS-FNA, we propose a sequential approach for detecting KRAS mutations using mutant enriched-PCR (ME-PCR, sensitivity up to 0.1%) in cytologically indeterminate and negative samples tested wild-type by RT-qPCR. EUS-FNA specimens from 107 patients with pancreatic masses (51 males, 56 females, mean age 67 years) were cytologically examined. According to the Papanicolaou Society of Cytopathology guidelines, 50 cases (47%) were classified malignant, 15 (14%) suspicious, 13 (12%) atypical and 10 (9%) negative for malignancy; 18 cases (17%) were non-diagnostic. The overall specificity and sensitivity of cytological examination were 100% and 61%, respectively, when only negative and positive cases were considered; when atypical and suspicious were added to positive cases, the sensitivity increased to 95.1% and the specificity decreased to 85.7%. In all the cases, DNA was extracted from the cell-block and KRAS mutations were investigated by RT-qPCR, followed by ME-PCR in non-amplifiable and negative cases. The overall sensitivity and specificity of KRAS mutation testing alone were 79.3% and 100%; when KRAS mutation testing was performed in indeterminate and negative cytology, the sensitivity increased to 90% with specificity to 100%. Our data indicate that conventional cytology from EUS-FNA samples is highly specific for the diagnosis of pancreatic cancer. Indeterminate and negative cases need to be screened for KRAS mutations; this two-step approach may greatly improve the diagnostic accuracy of this method.