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Aims: Loss of heterozygosity in chromosome 9p21, common in urothelial carcinoma (UC), typically involves deletion of CDKN2A and MTAP genes. MTAP loss is emerging as a promising therapeutic target and predictive biomarker in UC. This single-centrre retrospective study examined the incidence of CDKN2A deletions and MTAP loss in muscle-invasive bladder cancer (MIBC) and metastatic urothelial carcinoma (mUC), investigating their correlations with clinical, pathological, and genomic features, as well as patient outcomes., Methods: Fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) were performed on 302 MIBC specimens and 63 biopsy-proven metachronous urothelial metastases to assess CDKN2A deletions and MTAP protein expression., Results: CDKN2A homozygous deletion (HD), identified in 30.3% of MIBCs, and MTAP loss, found in 28.8% of MIBCs, were both significantly associated with the luminal-URO subtype, FGFR3 mutations, and normal/wildtype p53 IHC (P < 0.05). Loss of MTAP expression was significantly correlated with CDKN2A HD, with 84.0% sensitivity, 92.3% negative predictive value (NPV), 96.3% specificity, and 91.9% positive predictive value (PPV). MTAP expression was 100% concordant between primary tumours and nodal metastases. Patients with MTAP loss had a higher incidence of visceral metastases (50%) compared to bone/soft tissue (35.7%) and nodes (14.3%). Mean progression-free survival and overall survival were shorter for patients with MTAP loss, although not statistically significant., Conclusion: Our findings highlight CDKN2A HD and MTAP loss as prevalent genetic alterations in MIBC and mUC, particularly within the luminal-URO subtype and FGFR3-mutated, p53-normal/wildtype tumours. MTAP IHC can serve as a surrogate marker for 9p21.3 HD, highlighting its clinical relevance and potential as a therapeutic target and predictive biomarker in MIBC., (© 2024 The Author(s). Histopathology published by John Wiley & Sons Ltd.)

Aims: Our understanding of dedifferentiated endometrial carcinoma (DEC), a rare and aggressive malignancy, mainly reflects undifferentiated carcinomas (UC) arising in the setting of low-grade endometrial cancer (DEC-LG). However, cases of UC arising in the setting of high-grade EC (DEC-HG) have been noted in the literature. Our knowledge of the genomics of DEC-HG is limited. To characterise the molecular landscape of DEC-HC, targeted genomic sequencing and immunohistochemical analysis was carried out on seven DEC-HG and four DEC-LG., Methods and Results: DEC-HG and DEC-LG, including undifferentiated and differentiated components, both showed a similar frequency and spectrum of mutations. ARID1A mutations were identified in 6/7 (86%) DEC-HG and 4/4 (100%) DEC-LG, while SMARCA4 mutations were present in 4/7 (57%) DEC-HG and in 1/4 (25%) DEC-LG. Concurrent SMARCA4/BRG1 protein loss by immunohistochemistry was observed in 3/4 and 1/1 SMARCA4 mutated DEC-HG and DEC-LG, respectively. Neither genomic alterations nor protein loss in SMARCB1/INI1 were observed in any of our cases. TP53 mutations were detected in 4/7 (57%) DEC-HG and in 2/4 (50%) DEC-LG, while mutation-pattern p53 immunohistochemistry expression was observed in 2/7 (29%) DEC-HG and none of the DEC-LG. MLH1 mutations were observed in 1/7 (14%) DEC-HG and 1/4 (25%) DEC-LG. MSH2 and MSH6 mutations were each detected in 1/7 (14%) DEC-HG, but neither was associated with corresponding loss of protein expression., Conclusion: The findings support expanding the definition of DEC to include DEC-HG, a previously under-recognised phenomenon with genomic similarities to DEC-LG., (© 2023 The Authors. Histopathology published by John Wiley & Sons Ltd.)

Aims: To report novel observations in five mesonephric-like adenocarcinomas (MLAs) of the female genital tract., Methods and Results: We report two endometrial MLAs in association with endometrioid carcinoma and atypical hyperplasia and three (one endometrial, two ovarian) cases with a sarcomatoid component (mesonephric-like carcinosarcoma). Pathogenic KRAS mutations, which are characteristic of MLA, were identified in all cases although interestingly, in one of the mixed carcinomas, this was confined to the endometrioid component. The concurrent MLA, endometrioid carcinoma and atypical hyperplasia components in one case harboured identical EGFR, PTEN and CCNE1 mutations, suggesting that the atypical hyperplasia gave rise to a Müllerian carcinoma with both endometrioid and mesonephric-like components. The carcinosarcomas all contained a component of MLA and a sarcomatous component with chondroid elements. In the ovarian carcinosarcomas, the coexisting epithelial and sarcomatous components shared some mutations including KRAS and CREBBP, suggesting that they are clonally related. Furthermore, in one case CREBBP and KRAS mutations detected in the MLA and sarcomatous components were also detected in an associated undifferentiated carcinoma component, suggesting that it was clonally related to the MLA and sarcomatous components., Conclusions: Our observations provide additional evidence that MLAs have a Müllerian origin and characterise mesonephric-like carcinosarcomas in which chondroid elements appear to be characteristic. In reporting these findings, we provide recommendations for distinction between a mesonephric-like carcinosarcoma and a MLA with a spindle cell component., (© 2023 The Authors. Histopathology published by John Wiley & Sons Ltd.)

Background: The pattern-based (Silva) classification of invasive human papilloma virus (HPV)-associated endocervical adenocarcinomas (HPVA) is an established and reproducible method to predict outcomes for this otherwise stage-dependent group of tumours. Previous studies utilising targeted sequencing have shown a correlation between mutational profiles and an invasive pattern. However, such correlation has not been explored using comprehensive molecular testing., Design: Clinicopathologic data including invasive pattern (Silva groups A, B, and C) was collected for a cohort of invasive HPVA, which previously underwent massive parallel sequencing using a panel covering 447 genes. Pathogenic alterations, molecular signatures, tumour mutational burden (TMB), and copy number alterations (CNA) were correlated with pattern of invasion., Results: Forty five HPVA (11 pattern A, 17 pattern B, and 17 pattern C tumours) were included. Patients with pattern A presented at stage I with no involved lymph nodes or evidence of recurrence (in those with >2 months of follow-up). Patterns B and C patients also mostly presented at stage I with negative lymph nodes, but had a greater frequency of recurrence; 3/17 pattern B and 1/17 pattern C HPVAs harboured lymphovascular space invasion (LVI). An APOBEC mutational signature was detected only in Silva pattern C tumours (5/17), and pathogenic PIK3CA changes were detected only in destructively invasive HPVA (patterns B and C). When cases were grouped as low-risk (pattern A and pattern B without LVI) and high-risk (pattern B with LVI and pattern C), high-risk tumours were enriched in mutations in PIK3CA, ATRX, and ERBB2. There was a statistically significant difference in TMB between low-risk and high-risk pattern tumours (P = 0.006), as well as between Pattern C tumours with and without an APOBEC signature (P = 0.002). CNA burden increased from pattern A to C., Conclusion: Our findings further indicate that key molecular events in HPVA correlate with the morphologic invasive properties of the tumour and their aggressiveness. Pattern B tumours with LVI clustered with pattern C tumours, whereas pattern B tumours without LVI approached pattern A genotypically. Our study provides a biologic foundation for consolidating the Silva system into low-risk (pattern A + B without LVI) and high-risk (pattern B with LVI and pattern C) categories., (© 2023 John Wiley & Sons Ltd.)

Aims: Grading of primary ovarian mucinous carcinoma (OMC) is inconsistent among practices. The International Collaboration on Cancer Reporting recommends grading OMC using the International Federation of Gynecology and Obstetrics (FIGO) system for endometrial endometrioid carcinoma, when needed. The growth pattern (expansile versus infiltrative), a known prognostic variable in OMC, is not considered in any grading system. We herein analysed the prognostic value of various grading methods in a well-annotated cohort of OMC., Methods and Results: Institutional OMCs underwent review and grading by the Silverberg and FIGO schemes and a novel system, growth-based grading (GBG), defined as G1 (expansile growth or infiltrative invasion in ≤10%) and G2 (infiltrative growth >10% of tumour). Of 46 OMCs included, 80% were FIGO stage I, 11% stage II and 9% stage III. On follow-up (mean = 52 months, range = 1-190), five patients (11%) had adverse events (three recurrences and four deaths). On univariate analysis, stage (P = 0.01, Cox proportional analysis), Silverberg grade (P = 0.01), GBG grade (P = 0.001) and percentage of infiltrative growth (P < 0.001), but not FIGO grade, correlated with disease-free survival. Log-rank analysis showed increased survival in patients with Silverberg grade 1 versus 2 (P < 0.001) and those with GBG G1 versus G2 (P < 0.001). None of the parameters evaluated was significant on multivariate analysis (restricted due to the low number of adverse events)., Conclusions: Silverberg and the new GBG system appear to be prognostically significant in OMC. Pattern-based grading allows for a binary stratification into low- and high-grade categories, which may be more appropriate for patient risk stratification. Despite current practices and recommendations to utilise FIGO grading in OMC, our study shows no prognostic significance of this system and we advise against its use., (© 2020 John Wiley & Sons Ltd.)