Molecular analysis using SalvGlandDx improves risk of malignancy estimation and diagnosis of salivary gland cytopathology: An exploratory multicenter study.

BACKGROUND: Diagnosis of salivary gland neoplasms is challenging, especially on cytological specimens acquired by fine-needle aspiration. The recently implemented standardized Milan system for reporting salivary gland cytopathology provides an estimated risk of malignancy (ROM); yet, for two of the categories, the diagnosis of the lesion remains unclear. However, a precise diagnosis is desirable for optimal patient management, including planning of surgery and imaging procedures. METHODS: Cytological specimens (n = 106) were subjected to molecular analysis using the SalvGlandDx panel. The risk of malignancy was calculated for each detected alteration based on the diagnosis of the resection specimen. By taking into account the molecular alterations, their associated ROM, the clinical and cytological features, and the current literature, the Milan category was evaluated. RESULTS: Of n = 63 technically valid cases, 76% revealed a molecular alteration. A total of 94% of these molecularly altered cases could be assigned to a different Milan category when additionally taking molecular results into account. In only 2% of the salivary gland neoplasms of uncertain malignant potential, in which a molecular alteration was detected, the classification remained salivary gland neoplasms of uncertain malignant potential. CONCLUSION: Molecular analysis of cytological specimens provides a benefit in classifying salivary gland neoplasms on fine-needle aspiration. It can improve the ROM estimation and thus help to assign cases of formerly unknown malignant potential to clearly benign or malignant categories.

Enrichment of colibactin-associated mutational signatures in unexplained colorectal polyposis patients.

BACKGROUND: Colibactin, a genotoxin produced by polyketide synthase harboring (pks+) bacteria, induces double-strand breaks and chromosome aberrations. Consequently, enrichment of pks+Escherichia coli in colorectal cancer and polyposis suggests a possible carcinogenic effect in the large intestine. Additionally, specific colibactin-associated mutational signatures; SBS88 and ID18 in the Catalogue of Somatic Mutations in Cancer database, are detected in colorectal carcinomas. Previous research showed that a recurrent APC splice variant perfectly fits SBS88. METHODS: In this study, we explore the presence of colibactin-associated signatures and fecal pks in an unexplained polyposis cohort. Somatic targeted Next-Generation Sequencing (NGS) was performed for 379 patients. Additionally, for a subset of 29 patients, metagenomics was performed on feces and mutational signature analyses using Whole-Genome Sequencing (WGS) on Formalin-Fixed Paraffin Embedded (FFPE) colorectal tissue blocks. RESULTS: NGS showed somatic APC variants fitting SBS88 or ID18 in at least one colorectal adenoma or carcinoma in 29% of patients. Fecal metagenomic analyses revealed enriched presence of pks genes in patients with somatic variants fitting colibactin-associated signatures compared to patients without variants fitting colibactin-associated signatures. Also, mutational signature analyses showed enrichment of SBS88 and ID18 in patients with variants fitting these signatures in NGS compared to patients without. CONCLUSIONS: These findings further support colibactins ability to mutagenize colorectal mucosa and contribute to the development of colorectal adenomas and carcinomas explaining a relevant part of patients with unexplained polyposis.

Clinicogenomic associations in childhood Langerhans cell histiocytosis: an international cohort study.

Langerhans cell histiocytosis (LCH) is a rare neoplastic disorder caused by somatic genetic alterations in hematopoietic precursor cells differentiating into CD1a+/CD207+ histiocytes. LCH clinical manifestation is highly heterogeneous. BRAF and MAP2K1 mutations account for ∼80% of genetic driver alterations in neoplastic LCH cells. However, their clinical associations remain incompletely understood. Here, we present an international clinicogenomic study of childhood LCH, investigating 377 patients genotyped for at least BRAFV600E. MAPK pathway gene alterations were detected in 300 (79.6%) patients, including 191 (50.7%) with BRAFV600E, 54 with MAP2K1 mutations, 39 with BRAF exon 12 mutations, 13 with rare BRAF alterations, and 3 with ARAF or KRAS mutations. Our results confirm that BRAFV600E associates with lower age at diagnosis and higher prevalence of multisystem LCH, high-risk disease, and skin involvement. Furthermore, BRAFV600E appeared to correlate with a higher prevalence of central nervous system (CNS)-risk bone lesions. In contrast, MAP2K1 mutations associated with a higher prevalence of single-system (SS)-bone LCH, and BRAF exon 12 deletions seemed to correlate with more lung involvement. Although BRAFV600E correlated with reduced event-free survival in the overall cohort, neither BRAF nor MAP2K1 mutations associated with event-free survival when patients were stratified by disease extent. Thus, the correlation of BRAFV600E with inferior clinical outcome is (primarily) driven by its association with disease extents known for high rates of progression or relapse, including multisystem LCH. These findings advance our understanding of factors underlying the remarkable clinical heterogeneity of LCH but also question the independent prognostic value of lesional BRAFV600E status.

The sensitivity of pan-TRK immunohistochemistry in solid tumours: A meta-analysis.

INTRODUCTION: Since the approval of neurotrophic tropomyosin receptor kinase (NTRK) tyrosine kinase inhibitors for fist-line advanced stage pan-cancer therapy, pathologists and molecular biologists have been facing a complex question: how should the large volume of specimens be screened for NTRK fusions? Immunohistochemistry is fast and cheap, but the sensitivity compared to RNA NGS is unclear. METHODS: We performed RNA-based next-generation sequencing on 1,329 cases and stained 24 NTRK-rearranged cases immunohistochemically with pan-TRK (ERP17341). Additionally, we performed a meta-analysis of the literature. After screening 580 studies, 200 additional NTRK-rearranged cases from 13 studies, analysed with sensitive molecular diagnostics as well as pan-TRK IHC, were included. RESULTS: In the included 224 NTRK-rearranged solid tumours, the sensitivity for pan-TRK IHC was 82% and the false-negative rate was 18%. NTRK3 fusions had more false negatives (27%) compared to NTRK1 (6%) and NTRK2 (14%) (p = 0.0006). Membranous, nuclear and peri-nuclear staining patterns strongly correlated with different fusion products, with membranous staining being more prevalent in NTRK1 and NTRK2, nuclear in NTRK3, and perinuclear in NTRK1. CONCLUSION: Despite a reduction in the number of molecular analysis, using pan-TRK immunohistochemistry as a prescreening method to detect NTRK fusions in solid tumours will miss 18% of all NTRK-fused cases (especially involving NTRK3). Therefore, the most comprehensive and optimal option to detect NTRK fusions is to perform molecular testing on all eligible cases. However, in case of financial or logistical limitations, an immunohistochemistry-first approach is defensible in tumours with a low prevalence of NTRK fusions.

Mismatch repair deficiency and MUTYH variants in small intestine-neuroendocrine tumors.

Small intestine-neuroendocrine tumors (SI-NETs) are one of the most common tumors of the small bowel. Despite an increasing incidence, the exact mechanisms driving underlying pathology remain to be determined. Interestingly, recent studies linked the development of (SI-)NETs to both Lynch syndrome (LS) and MUTYH variants. If confirmed, these associations would have important consequences for treatment. In this study we therefore investigated the prevalence of mismatch repair (MMR) deficiency and MUTYH variants in 64 primary resected SI-NETs. Immunohistochemistry was used to assess the expression of the MMR genes, and competitive allele-specific PCR (KASPar) targeting two hotspot MUTYH variants [p.(Tyr179Cys), p.(Gly396Asp)] was performed to determine their prevalence in SI-NETs. Strikingly, all 64 SI-NETs stained positive for MSH6 and PMS2, indicating MMR proficiency. In addition, no MUTYH hotspot variant was found in any of the 64 SI-NETs. As such, these results do not support an association between SI-NET development and LS or MUTYH variants. In order to gain insight into SI-NET pathogenesis and optimally manage patients, future research should therefore focus on other candidate genes.

Prevalence of mismatch repair deficiency and Lynch syndrome in a cohort of unselected small bowel adenocarcinomas.

AIMS: Previous estimates of the prevalence of mismatch repair (MMR) deficiency and Lynch syndrome in small bowel cancer have varied widely. The aim of this study was to establish the prevalence of MMR deficiency and Lynch syndrome in a large group of small bowel adenocarcinomas. METHODS: To this end, a total of 400 small bowel adenocarcinomas (332 resections, 68 biopsies) were collected through the Dutch nationwide registry of histopathology and cytopathology (Pathologisch-Anatomisch Landelijk Geautomatiseerd Archief (PALGA)). No preselection criteria, such as family history, were applied, thus avoiding (ascertainment) bias. MMR deficiency status was determined by immunohistochemical staining of MMR proteins, supplemented by MLH1 promoter hypermethylation analysis and next generation sequencing of the MMR genes. RESULTS: MMR deficiency was observed in 22.3% of resected and 4.4% of biopsied small bowel carcinomas. Prevalence of Lynch syndrome was 6.2% in resections and 0.0% in biopsy samples. Patients with Lynch syndrome-associated small bowel cancer were significantly younger at the time of diagnosis than patients with MMR-proficient and sporadic MMR-deficient cancers (mean age of 54.6 years vs 66.6 years and 68.8 years, respectively, p<0.000). CONCLUSIONS: The prevalence of MMR deficiency and Lynch syndrome in resected small bowel adenocarcinomas is at least comparable to prevalence in colorectal cancers, a finding relevant both for treatment (immunotherapy) and family management. We recommend that all small bowel adenocarcinomas should be screened for MMR deficiency.