Richard Colling

Traditional serrated adenomas (TSAs) admixed with other serrated (so-called precursor) polyps and conventional adenomas: a frequent occurrence

Background Traditional serrated adenoma (TSA) is a very characteristic type of serrated polyp that has a predilection for the left colon. Recent molecular advances have shown two molecular phenotypes of TSA: one associated with BRAF mutations and the other with KRAS mutations. The former is associated with hyperplastic polyps (HPs) and sessile serrated adenomas (SSAs), while the latter is associated with more conventional adenomatous dysplasia. Aims The association of TSAs with so-called precursor lesions (HPs and SSAs) is not well recognised and the purpose of this study was to explore the coexistent presence of HPs, SSAs and adenomatous polyps within a large cohort of TSAs. Methods In total 149 TSAs were examined for the presence of HP, SSA and adenomatous polyps. Results Seen in 83 men and 65 women ranging in age from 32 to 89 years and 127 were left sided with 22 in the right colon. Seventy-eight of the 149 TSAs showed evidence of another polyp (52.34%): 32 were low-grade tubular/tubulovillous adenomas (TAs/TVAs; 41%), 28 were HPs (36%) and 18 were SSAs (23%). Eleven of the 22 right-sided TSAs were associated with a precursor lesion (1 HP and 7 SSA). In addition, five TSAs showed more than one polyp type: TSA with TA/TVA and HP (3); TSA with TA/TVA and SSA (2). The TAs/TVAs were adjacent to the TSA but occurred as a separate discrete polyp, while HPs and SSAs were intermingled with the TSA and present at the base and surface of the lesion. Conclusions More than 50% of TSAs are associated with a precursor lesion or adjacent TA/TVA. Their recognition is important as this may have surveillance and management ramifications.

Histological overlap between colorectal villous/tubulovillous and traditional serrated adenomas.

To ascertain the degree of histological overlap between conventional villous/tubulovillous (VA/TVAs) and traditional serrated adenomas (TSA).

Automated PCR detection of BRAF mutations in colorectal adenocarcinoma: a diagnostic test accuracy study

Background Testing for BRAF mutations in colorectal carcinoma (CRC) is important in the screening pathway for Lynch syndrome and is of prognostic value to guide management. This is a diagnostic accuracy study of the Idylla system, a novel and automated alternative PCR system. Methods 100 consecutive formalin-fixed, paraffin-embedded CRC resection cases were tested for BRAF mutations using the Idylla automated platform and compared with standard (Cobas) PCR. Results The sensitivity of the Idylla BRAF test was 100% and the specificity was 96%. Only one discordant Idylla positive/standard PCR negative result occurred and on Droplet Digital PCR demonstrated a mutation not identified by traditional PCR in this case. Conclusion This study has validated the Idylla system for BRAF testing in CRC and demonstrated a possibly greater sensitivity, in addition to cost effectiveness and shorter turnaround time, when compared with standard PCR.

Validating a fully automated real-time PCR-based system for use in the molecular diagnostic analysis of colorectal carcinoma: a comparison with NGS and IHC

Background Molecular testing is increasingly needed in colorectal carcinoma (CRC) and the current clinically relevant mutations are in BRAF, KRAS and NRAS. This study aimed to further validate a new alternative polymerase chain reaction (PCR) platform (Idylla, Biocartis) against existing next-generation sequencing (NGS) and immunohistochemistry (IHC) assays. Methods 56 Idylla tests were performed on 43 CRC cases, in a total of 74 comparisons against an NGS panel (Ion Torrent) and the VE1 (anti-BRAF) antibody IHC. Discrepant cases were also compared with either conventional (Cobas) or droplet digital PCR (Bio-Rad). Results Idylla showed an overall concordance of 100% (95% CI 93% to 100%) with comparator molecular testing and indications were that Idylla is likely to be more sensitive than routine NGS. BRAF IHC showed 90% concordance with NGS (95% CI 70% to 97%). Conclusions This study validates Idylla in formalin-fixed, paraffin-embedded CRC tissue. BRAF IHC, however, is an unreliable substitute for molecular testing in CRC.

Multi-Center Evaluation of the Fully Automated PCR-Based Idylla™ KRAS Mutation Assay for Rapid KRAS Mutation Status Determination on Formalin-Fixed Paraffin-Embedded Tissue of Human Colorectal Cancer.

Since the advent of monoclonal antibodies against epidermal growth factor receptor (EGFR) in colorectal cancer therapy, the determination of RAS mutational status is needed for therapeutic decision-making. Most prevalent in colorectal cancer are KRAS exon 2 mutations (40% prevalence); lower prevalence is observed for KRAS exon 3 and 4 mutations (6%) and NRAS exon 2, 3, and 4 mutations (5%). The Idylla™ KRAS Mutation Test on the molecular diagnostics Idylla™ platform is a simple (<2 minutes hands-on time), highly reliable, and rapid (approximately 2 hours turnaround time) in vitro diagnostic sample-to-result solution. This test enables qualitative detection of 21 mutations in codons 12, 13, 59, 61, 117, and 146 of the KRAS oncogene being clinically relevant according to the latest clinical guidelines. Here, the performance of the Idylla™ KRAS Mutation Assay, for Research Use Only, was assessed on archived formalin-fixed paraffin-embedded (FFPE) tissue sections by comparing its results with the results previously obtained by routine reference approaches for KRAS genotyping. In case of discordance, samples were assessed further by additional methods. Among the 374 colorectal cancer FFPE samples tested, the overall concordance between the Idylla™ KRAS Mutation Assay and the confirmed reference routine test results was found to be 98.9%. The Idylla™ KRAS Mutation Assay enabled detection of 5 additional KRAS-mutated samples not detected previously with reference methods. As conclusion the Idylla™ KRAS Mutation Test can be applied as routine tool in any clinical setting, without needing molecular infrastructure or expertise, to guide the personalized treatment of colorectal cancer patients.

Discrepancy rates in liver biopsy reporting

Medical liver biopsy reporting is challenging, and maintaining competency with small case numbers is potentially difficult. This study evaluates the discrepancies identified in cases referred to a specialist centre between the specialist reports and those of the referring general departments. Fifty consecutive recently referred cases were selected, and original and final reports were compared. Discrepancies were classified as per the Royal College of Pathologists guidelines and scored for potential clinical impact. The overall rate of discrepancy was 38% with most of these due to differences in interpretation of morphology. Seventy per cent of these discrepancies were judged to have major clinical impact (26% of all referred cases). This study highlights the need for robust systems of quality control of liver biopsies in a general setting.

Bile duct basement membrane thickening in primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC) is characterized histologically by portal inflammation, bile duct injury and regeneration and concentric periductal fibrosis. Although seen commonly in our experience, the significance of histological thickening of the bile duct basement membrane on periodic acid Schiff (PAS)‐positive, diastase‐resistant (DPAS) staining has never been analysed formally. In this paper we provide an evidence‐based assessment of basement membrane thickening (BMT) reproducibility and diagnostic accuracy.

A study of α5 chain of collagen IV, caldesmon, placental alkaline phosphatase and smoothelin as immunohistochemical markers of gastrointestinal smooth muscle neoplasms

Aims The histological distinction between gastrointestinal smooth muscle neoplasms (SMNs) and their differential diagnoses, especially gastrointestinal stromal tumours (GISTs), has important clinical management implications. This study aimed to investigate preliminary data suggesting that loss of the α5 chain of collagen IV (α5(IV)), placental acid phosphatase (PLAP) expression and smoothelin expression can be used diagnostically as markers of gastrointestinal SMNs. To aid this investigation, these potential markers were directly compared against caldesmon. Methods 31 SMNs and 111 potential differential diagnoses (16 different neoplasm types) were immunostained for caldesmon, PLAP and smoothelin. Results A pilot study indicated that loss of α5(IV) positivity was neither a specific nor sensitive marker of SMN. Caldesmon, PLAP and smoothelin were expressed by all 31 SMNs though leiomyosarcomas showed some loss of staining proportion and/or intensity. Caldesmon positivity was commonly shown by GISTs, glomus tumours and angiomyolipomas. Cytoplasmic smoothelin positivity was commonly shown by glomus tumours and angiomyolipomas, whereas PLAP positivity was shown by one desmoplastic small round cell tumour studied and only infrequently shown by angiomyolipomas. Nuclear smoothelin positivity was seen among four leiomyosarcomas but also a wide range of non-SMNs. Conclusions α5(IV) immunohistochemistry with the A7 antibody is not a diagnostically useful marker of gastrointestinal SMNs. Both PLAP and smoothelin (cytoplasmic expression only) are as sensitive as but are more specific than caldesmon as such a marker. Further, PLAP and smoothelin immunostainings are technically reliable and can be reproducibly assessed.

Intraoperative identification and analysis of lymph nodes at laparoscopic colorectal cancer surgery using fluorescence imaging combined with rapid OSNA pathological assessment

BackgroundStandard surgical practice for colorectal cancer involves resection of the primary lesion and all draining lymph nodes. Accurate intraoperative assessment of nodal status could allow stratified resectional extent. One-step nucleic acid (OSNA) can provide a rapid method of interrogating nodal tissue, whilst near-infrared (NIR) laparoscopy together with indocyanine green (ICG) can identify relevant nodal tissue intraoperatively.MethodsICG was administered around the tumour endoscopically prior to the operation. Fluorescent nodes identified by NIR were marked and submitted for whole-node OSNA analysis. Further fresh lymph nodes dissected from the standard resection specimen were examined and analysed by both conventional histology and OSNA. In addition, the status of the fluorescent nodes was compared to that of non-ICG nodes to assess their predictive value.ResultsSixteen patients were recruited with a total final lymph node count of 287. 78 fresh lymph nodes were identified on fresh dissection for both histological and OSNA assessment with an analytical concordance rate of 98.7% (77/78). OSNA sensitivity was 1 (0.81–1, 95% CI) and specificity 0.98 (0.91–1, 95% CI). Six patients had a total of nine nodes identified intraoperatively by ICG fluorescence. Of these nine nodes, one was positive for metastasis on OSNA. OSNA analysis of the ICG-labelled node matched the final histological nodal stage in 3/6 patients (two being N0 and one N1). The final pathological nodal stage of the other three was N1 or N2, while the ICG nodes were negative.ConclusionOSNA is highly concordant with standard histology, although only a minority of nodes identifiable by full pathological analysis were found for OSNA on fresh dissection. OSNA can be combined with NIR and ICG lymphatic mapping to provide intraoperative assessment of nodal tissue in patients with colorectal cancer.

Mucin-rich variant of traditional serrated adenoma: a distinct morphological variant.

Traditional serrated adenomas (TSAs) account for 5% of serrated polyps, and have a villiform architecture, eosinophilic cells with a brush border, and indented, flat‐topped luminal serrations. However, some are composed of mucin‐filled goblet cells (GCs): mucin‐rich TSA (MrTSA). The aim of this study was to determine whether this variant has unique features as compared with classic TSA (cTSA).