Genetic Profiling Uncovers Genome-Wide Loss of Heterozygosity and Provides Insight into Mechanisms of Sarcomatoid Transformation in Chromophobe Renal Cell Carcinoma.

Sarcomatoid transformation occurs in ∼8% of chromophobe renal cell carcinoma (chRCC) and is associated with aggressive clinical behavior. In recent years, several studies have identified genomic, transcriptomic, and epigenomic correlates of aggressive behavior in chRCC; however, the molecular mechanisms associated with sarcomatoid transformation remain incompletely understood. In this study, we analyzed paired conventional and sarcomatoid histologic components of individual chRCC to elucidate the genomic alterations that underlie sarcomatoid transformation in this tumor type. Massively parallel sequencing was performed on paired (conventional and sarcomatoid) components from 8 chRCCs. All cases harbored TP53 variants (87.5% showing TP53 variants in both components and 12.5% only in the sarcomatoid component). Intratumor comparisons revealed that TP53 variants were concordant in 71% and discordant in 29% of cases. Additional recurrent single-nucleotide variants were found in RB1 (37.5% of cases) and PTEN (25% of cases), with the remaining single-nucleotide variants detected in these tumors (PBRM1, NF1, and ASXL1) being nonrecurrent. Copy number variant analysis showed the characteristic pattern of chromosomal losses associated with chRCC (1, 2, 6, 10, 13, 17, and 21) in the conventional histologic components only. Interestingly, the sarcomatoid components of these tumors demonstrated widespread loss of heterozygosity but lacked the above chromosomal losses, likely as a consequence of whole-genome duplication/imbalanced chromosomal duplication events. Overall, the findings suggest that TP53 variants followed by whole-genome duplication/imbalanced chromosomal duplication events underlie sarcomatoid transformation in chRCC.

Beta-Catenin Alterations in Postchemotherapy Yolk Sac Tumor, Postpubertal-Type With Enteroblastic Features.

Postchemotherapy postpubertal-type yolk sac tumors (YST) with glandular and solid phenotypes are aggressive and commonly resistant to systemic chemotherapy. These neoplasms show morphologic features that significantly overlap with those of somatic carcinomas with "enteroblastic" or "fetal" phenotype (the preferred terminology depends on the site of origin). They often present as late or very late recurrences, and their diagnosis is challenging because they frequently affect patients in an age group at risk for carcinomas of somatic origin. Recently, we incidentally identified examples of postchemotherapy glandular and solid YST with "enteroblastic" phenotypes and nuclear expression of beta-catenin, prompting us to further evaluate the prevalence of this phenomenon. We found nuclear expression of beta-catenin in 10 (29%) of 34 such tumors. A subset of cases with nuclear beta-catenin expression was further analyzed with a DNA sequencing panel (n = 6) and fluorescence in situ hybridization for isochromosome 12p [i(12p); n = 5]. Sequencing identified exon 3 CTNNB1 variants in 3 (50%) of 6 analyzed cases, and fluorescence in situ hybridization was positive for i(12p) in 5 of 5 cases. In conclusion, a significant subset of postchemotherapy YST with glandular or solid architecture and "enteroblastic" phenotype demonstrates beta-catenin alterations, suggesting that activation of Wnt signaling may play a role in the progression of these neoplasms. Moreover, nuclear beta-catenin expression in these tumors represents a potential diagnostic pitfall given that carcinomas of true somatic origin with overlapping morphology may also be positive for this marker.

Carcinoma arising in ileal conduit or orthotopic ileal neobladder reconstruction: A 20-year single institute experience.

CONTEXT: Carcinomas found in urinary diversion specimens are uncommon, particularly new primary tumours. New primary tumours primarily occur when the large intestine is utilised, whereas the occurrence is infrequent with the use of the ileum. These tumours include both the recurrence of primary malignancy or the development of a new primary malignancy originating from the small intestine. DESIGN: A search was performed within the pathology laboratory system to identify cases of malignancies involving ileal conduit/reconstruction from 2002 to 2022. Data on demographics, clinical details, pathology and management was recorded. RESULTS: A total of 13 male patients, with a mean age of 67 years (range = 49-81 years) were included in the study. The initial procedure performed included cystoprostatectomy (n = 10, including one case with right nephroureterectomy) and cystectomy (n = 3, including one case for bladder exstrophy) for initial diagnoses including urothelial carcinoma (n = 11; conventional, 6; sarcomatoid, 1; glandular 1; plasmacytoid, 1; micropapillary, 2) and adenocarcinoma (n = 1). The initial management included radical surgery with neoadjuvant chemotherapy/immunotherapy (n = 1), adjuvant chemotherapy (n = 3), intravesical adjuvant BCG (n = 2) and intravesical adjuvant chemotherapy (n = 1). Malignancies in ileal conduit or orthotopic ileal neobladder included recurrent urothelial carcinoma (n = 10) and new secondary adenocarcinomas (n = 3), which developed as early as 3 months (usually recurrence) and up to 13, 33 and 45 years (new primary malignancy) following primary resection. CONCLUSIONS: Utilising the ileum as conduit/neobladder presents a viable alternative for urinary diversion with a reduced malignancy risk compared to using a segment of the large intestine. However, there remains a potential for malignancy, either tumour recurrence or a new primary malignancy. In our study, tumour recurrence occurred up to 4 years following the initial diagnosis and the development of a new primary malignancy occurred up to 45 years after the initial diagnosis. Consequently, it is crucial to prioritise long-term follow-up for these patients undergoing this procedure.

ß-Catenin alterations in testicular Leydig cell tumour: a immunohistochemical and molecular analysis.

BACKGROUND: Testicular Leydig cell tumours (LCTs) are the most common type of sex cord-stromal tumour in men, representing 1%-3% of all testicular neoplasms. Among testicular sex cord-stromal tumours, CTNNB1 mutations and nuclear expression of ß-catenin have been typically associated with Sertoli cell tumour. Recent genomic analyses have shown that CTNNB1 variants are also identified in a subset of LCTs; however, the frequency and clinicopathologic associations of ß-catenin alterations remain incompletely understood in this tumour type. METHODS: In this study, we evaluated 32 LCTs (five malignant/metastasizing, 27 nonmetastasizing) using ß-catenin immunohistochemistry and DNA sequencing. RESULTS: Immunohistochemistry revealed focal or multifocal nuclear ß-catenin expression in 47% of the tumours. Diffuse nuclear ß-catenin expression (in >50% of the tumour cells) was not detected in any of the cases analysed herein. Comparison of ß-catenin-positive and ß-catenin-negative cases did not show significant differences in the frequency of adverse histopathologic findings or malignant clinical behaviour. DNA sequencing performed de novo on a subset of seven cases revealed the presence of exon 3 CTNNB1 variants in four of them (4/7, 57%), with variant allele frequencies (VAF) ranging from 7 to 33%. Two additional ß-catenin-positive cases that had been sequenced as part of a previous study harboured exon 3 CTNNB1 variants at VAF of 28% and 7%, respectively. CONCLUSION: These results demonstrate that ß-catenin alterations are relatively common in LCT, most likely occurring as subclonal events that are not enriched in cases with aggressive features. Further studies are needed to clarify the oncogenic role of ß-catenin in this tumour type.

Genomic analysis of primary epithelial neoplasms of the seminal vesicle identifies a subset of mucinous cystic tumours driven by KRAS mutations.

BACKGROUND: Carcinomas of the seminal vesicle are exceedingly rare, with a limited number of cases described in the literature. Reported cases span a relatively wide morphological spectrum, and their genomic features remain unexplored. DESIGN: In this study, we interrogated five primary epithelial neoplasms of the seminal vesicle using a targeted DNA sequencing platform (OncoPanel, 447 genes). RESULTS: The tumours included one adenocarcinoma with intestinal phenotype presenting after external beam radiation (for prostatic adenocarcinoma), one carcinoma with Müllerian-type clear cell phenotype, two mucinous tumours resembling low-grade mucinous neoplasms of the appendix (LAMN) and one mucinous cystadenoma. The post-radiation mucinous adenocarcinoma had genomic findings consistent with bi-allelic inactivation of TP53, as well as multiple copy-number changes with regional and chromosomal arm-level copy-number losses. The Müllerian-type clear cell carcinoma exhibited a complex copy-number profile with numerous regional and arm-level copy-number changes, as well as focal amplification events, including copy-number gain of 8q and amplification of a region within 20q13. Both low-grade mucinous tumours resembling LAMN harboured hot-spot gain-of-function KRAS variants (p.G12V and p.G13D) as the only genomic alteration. No genomic alterations were detected inthe lesion diagnosed as mucinous cystadenoma. CONCLUSION: Our results suggest that primary low-grade mucinous neoplasms of the seminal vesicle may represent a distinct entity equivalent to appendiceal counterparts, driven by gain-of-function variants of RAS GTPases. The remaining tumours showed genomic features that closely resembled those of neoplasms with comparable phenotypes and/or biological characteristics arising in other sites, suggesting that they could be managed similarly, with special considerations related to their anatomical location.

Evolution of Testicular Germ Cell Tumors in the Molecular Era With Histogenetic Implications.

The current WHO classification of testicular germ cell tumors is based on the pathogenesis of the tumors driven by different genomic events. The germ cell neoplasia in situ is the precursor lesion for all malignant germ cell tumors. The current understanding of pathogenesis is that the developmental and environmental factors with the erasure of parental genomic imprinting lead to the development of abnormal gonocytes that settle in the "spermatogonial Niche" in seminiferous tubules. The abnormal primordial germ cells in the seminiferous tubules give rise to pre-GCNIS cells under the influence of TPSY and OCT4 genes. The whole genome duplication events give rise to germ cell neoplasia in situ, which further acquires alterations in 12p along with NRAS and KRAS mutations to produce seminoma. A subset of seminomas acquires KIT mutation and does not differentiate further. The remaining KIT-stable seminomas differentiate to nonseminomatous GCTs after obtaining recurrent chromosomal losses, epigenetic modification, and posttranscriptional regulation by multiple genes. Nonseminomatous germ cell tumors also develop directly from differentiated germ cell neoplasia in situ. TP53 pathway with downstream drivers may give rise to somatic-type malignancies of GCT. The GCTs are remarkably sensitive to cisplatin-based combination chemotherapy; however, resistance to cisplatin develops in up to 8% of tumors and appears to be driven by TP53/MDM2 gene mutations. Serum and Plasma miRNAs show promise in diagnosing, managing, and following up on these tumors. The mechanisms underlying the development of most tumors have been elucidated; however, additional studies are required to pinpoint the events directing specific characteristics. Advances in identifying specific molecular markers have been seen recently and may be adopted as gold standards in the future.

Contemporary Updates on Sex Cord-stromal Tumors of the Testis.

Testicular sex cord-stromal tumors (TSCSTs) are relatively rare, representing ~5% of testicular neoplasms overall. Historically, TSCSTs have been classified into 3 major entities: Leydig cell tumor, Sertoli cell tumor, and granulosa cell tumor. In recent years, immunophenotypic and molecular analyses have led to a more detailed understanding of the biological and genomic features of these neoplasms, resulting in the description of new entities, some of which have been included in the latest WHO classification. This review summarizes novel histopathologic, clinical, and molecular findings that may lead to a reappraisal of established concepts and help improve the diagnosis and clinical management of TSCSTs in the coming years.

Increased expression of proton pump and allergic inflammation genes predicts PPI failure in pediatric eosinophilic esophagitis.

Proton pump inhibitors (PPIs) are one of the standards of care of eosinophilic esophagitis (EoE) treatment, though PPI response rates are variable ranging from 23 to 63% in pediatric studies. We sought to determine if expression of select genes in esophageal mucosa can predict PPI responsiveness in EoE. Children with a new diagnosis of EoE (15 or more eosinophils/hpf on esophageal biopsy) were prospectively treated with 8 weeks of PPI therapy before follow-up esophagogastroduodenoscopy (EGD). Children with <15 eosinophils/hpf on follow-up were classified as having PPI-Responsive EoE (PPI-R) and ≥ 15 eosinophils/hpf as PPI-Nonresponsive EoE (PPI-NR). Using the Nanostring nCounter Analysis System, mRNA expression of a custom panel of genes was measured in esophageal biopsies. Immunohistochemical staining of biopsies was performed. Among children with EoE, 32% (8/25) had PPI-R EoE. ATP12A, ATP4A, tryptase-beta 2 (TPSB2), CLC and IL13 had higher expression in PPI-NR EoE compared to PPI-R EoE or controls. Immunohistochemical staining of ATP12A was higher among PPI-R EoE and PPI-NR EoE, compared to non-EoE controls. In this study, PPI-NR EoE had significantly higher baseline gene expression of mast cell, cytokine, proton pump, and eosinophil genes compared to PPI-R EoE. PPIs may be involved in an inflammatory cascade of mast cell activation that stimulates IL-13 release, which upregulates ATP12A and ATP4A that leads to eosinophil recruitment. Histologic PPI failure may occur when increased gene expression of these components is high and cannot be overcome pharmacologically, especially in the case of proton pump genes.

Testicular Juvenile Granulosa Cell Tumors Demonstrate Recurrent Loss of Chromosome 10 and Absence of Molecular Alterations Described in Ovarian Counterparts.

Testicular juvenile granulosa cell tumors (JGCTs) are a rare type of sex cord-stromal tumor, accounting for <5% of all neoplasms of the prepubertal testis. Previous reports have demonstrated sex chromosome anomalies in a small subset of cases, but the molecular alterations associated with JGCTs remain largely undescribed. We evaluated 18 JGCTs using massive parallel DNA and RNA sequencing panels. The median patient age was <1 month (range, newborn to 5 months). The patients presented with scrotal or intra-abdominal masses/enlargement, and all underwent radical orchiectomy (17 unilateral and 1 bilateral). The median tumor size was 1.8 cm (range, 1.3-10.5 cm). Histologically, the tumors were purely cystic/follicular or mixed (ie, solid and cystic/follicular). All cases were predominantly epithelioid, with 2 exhibiting prominent spindle cell components. Nuclear atypia was mild or absent, and the median number of mitoses was 0.4/mm2 (range, 0-10/mm2). Tumors frequently expressed SF-1 (11/12 cases, 92%), inhibin (6/7 cases, 86%), calretinin (3/4 cases, 75%), and keratins (2/4 cases, 50%). Single-nucleotide variant analysis demonstrated the absence of recurrent mutations. RNA sequencing did not detect gene fusions in 3 cases that were sequenced successfully. Recurrent monosomy 10 was identified in 8 of 14 cases (57%) with interpretable copy number variant data, and multiple whole-chromosome gains were present in the 2 cases with significant spindle cell components. This study demonstrated that testicular JGCTs harbor recurrent loss of chromosome 10 and lack the GNAS and AKT1 variants described in their ovarian counterparts.

Large cell calcifying Sertoli cell tumour: molecular and immunohistochemical assessment of a series comprising non-metastasising and metastasising neoplasms.

Large cell calcifying Sertoli cell tumour (LCCSCT) is a type of testicular sex cord-stromal tumour that may occur sporadically or in the context of Carney complex and other genetic syndromes. A subset is clinically malignant, and the molecular mechanisms that drive such aggressive behaviour remain unknown. METHODS AND RESULTS: We analysed 21 samples from 20 patients with LCCSCT (12 non-metastasising and eight metastasising) using PRKAR1A immunohistochemistry (IHC) and next-generation sequencing. All tumours except two (cases 17 and 20, both metastasising) demonstrated loss of PRKAR1A expression. Among 11 cases with interpretable sequencing results, all harboured pathogenic single nucleotide variants of PRKAR1A. Evidence of loss of heterozygosity (LOH) of PRKAR1A was present in all tumours with interpretable zygosity data, but the mechanisms of LOH were different for non-metastasising and metastasising tumours. Non-metastasising tumours demonstrated only copy-neutral LOH, while metastasising tumours demonstrated a spectrum of mechanisms of LOH, including copy-loss LOH, two concurrent mutations or copy-neutral LOH. Relevant molecular findings in non-metastasising LCCSCT were limited to PRKAR1A variants. In contrast, all metastasising LCCSCTs with interpretable data harboured additional pathogenic variants, including (but not restricted to) BRCA2 mutations with evidence of LOH and bi-allelic CDKN2A/B deletions. Three patients harboured PRKAR1A variants of inferred germline origin, including one with Carney complex and two without known syndromic features. CONCLUSIONS: This study further confirms that PRKAR1A IHC is a useful diagnostic tool for both non-metastasising and metastasising tumours and suggests that molecular analyses can be helpful to identify non-metastasising tumours with malignant potential in selected patients. Importantly, these results highlight that germline assessment could be beneficial for all patients presenting with LCCSCT.

Molecular correlates of male germ cell tumors with overgrowth of components resembling somatic malignancies.

A small subset of male germ cell tumors (GCT) demonstrates overgrowth of histologic components that resemble somatic malignancies (e.g., sarcoma, carcinoma). The presence of so-called "somatic-type" malignancies (SM) in GCT has been associated with chemotherapy-resistance and poor clinical outcomes in prior studies. However, the molecular characteristics of these tumors remain largely undescribed. In this study, we performed a multi-platform molecular analysis of GCTs with SM diagnosed in 36 male patients (primary site: testis, 29 and mediastinum, 7). The most common histologic types of SM were sarcoma and embryonic-type neuroectodermal tumor (ENT, formerly known as "PNET"), present in 61% and 31% of cases, respectively. KRAS and TP53 mutations were identified by DNA sequencing in 28% of cases each, with enrichment of TP53 mutations in mediastinal tumors (86%). Gains in the short arm of chromosome 12 were seen in 91% of cases, likely reflecting the presence of isochromosome 12p. Numerous copy number changes indicative of widespread aneuploidy were found in 94% of cases. Focal homozygous deletions and amplifications were also detected, including MDM2 amplifications in 16% of cases. Sequencing of paired samples in 8 patients revealed similar mutational and copy number profiles in the conventional GCT and SM components. Oncogenic gene fusions were not detected using RNA sequencing of SM components from 9 cases. DNA methylation analysis highlighted the distinct methylation profile of SM components that sets them apart from conventional GCT components. In conclusion, GCT with SM are characterized by widespread aneuploidy, a distinct epigenetic signature and the presence of mutations that are otherwise rare in testicular GCT without SM. The similarity of the mutational and DNA methylation profiles of different histologic types of SM suggests that the identification of SM components could be more important than their precise histologic subclassification, pending confirmation by further studies.

Clinicopathologic and molecular spectrum of testicular sex cord-stromal tumors not amenable to specific histopathologic subclassification.

A subset of testicular sex cord-stromal tumors (SCST), which includes neoplasms with mixed histology, cannot be classified into a specific histologic subtype. This study evaluated the clinicopathologic, immunophenotypic and molecular features of 26 SCST not amenable to specific classification by expert uropathologists. Median age at diagnosis was 43 years and median tumor size was 2.4 cm. Follow-up information was available for 18 (69%) patients, with evidence of an aggressive clinical course in 6 patients (4 alive with disease, 2 dead of disease 3 months and 6 months after orchiectomy). Microscopically, SCST not amenable to specific classification demonstrated monophasic epithelioid (9/26, 35%), monophasic spindle cell (5/26, 19%), and biphasic or mixed histology (12/26, 46%). One or more aggressive histopathologic features were seen in 11 cases. DNA sequencing was successful in 22 tumors. Pathogenic CTNNB1 and APC alterations were seen in 7 (33%) and 2 (10%) cases, respectively, with additional variants (e.g., CDKN2A, RB1, TP53, BRCA2) being identified in individual cases. Combined evaluation of morphology, sequencing data and beta-catenin immunohistochemistry resulted in reclassification of 6 (23%) tumors as Sertoli cell tumor, not otherwise specified. This was supported by comparing the methylation profiles of a subset of these tumors and those of typical Sertoli cell tumors. Additionally, a subset of 5 neoplasms (19%) with spindle cell or biphasic histology and SMA expression was characterized by hyperdiploid genomes with recurrent chromosomal gains and absence of driver mutations, possibly representing a distinct tumor type. The SCST that remained not amenable to specific histologic classification (15/26, 58%) were enriched for aggressive histologic features and malignant clinical behavior. In conclusion, this study demonstrated that a subset of testicular SCST that were originally not amenable to specific classification could be reclassified by combined evaluation of morphology, immunohistochemistry and molecular data.

Recurrent KRAS mutations are early events in the development of papillary renal neoplasm with reverse polarity.

We evaluated the clinicopathologic and molecular characteristics of mostly incidentally detected, small, papillary renal neoplasms with reverse polarity (PRNRP). The cohort comprised 50 PRNRP from 46 patients, divided into 2 groups. The clinically undetected (<5 mm) neoplasms (n = 34; 68%) had a median size of 1.1 mm (range 0.2-4.3 mm; mean 1.4 mm), and the clinically detected (≥5 mm) neoplasms (n = 16; 32%) which had a median size of 13 mm (range 9-30 mm; mean 16 mm). Neoplasms were positive for GATA3 (n = 47; 100%) and L1CAM (n = 34/38; 89%) and were negative for vimentin (n = 0/44; 0%) and, to a lesser extent, AMACR [(n = 12/46; 26%; weak = 9, weak/moderate = 3)]. KRAS mutations were found in 44% (n = 15/34) of the clinically undetected PRNRP and 88% of the clinically detected PRNRP (n = 14/16). The two clinically detected PRNRP with wild-type KRAS gene were markedly cystic and contained microscopic intracystic tumors. In the clinically undetected PRNRP, the detected KRAS mutations rate was higher in those measuring ≥1 mm vs <1 mm [n = 14/19 (74%) vs n = 1/15 (7%)]. Overall, the KRAS mutations were present in exon 2-codon 12: c.35 G > T (n = 21), c.34 G > T (n = 3), c.35 G > A (n = 2), c.34 G > C (n = 2) resulting in p.Gly12Val, p. Gly12Asp, p.Gly12Cys and p.Gly12Arg, respectively. One PRNRP had a G12A/V/D complex mutation. Twenty-six PRNRP were concurrently present with other tumors of different histologic subtypes in the ipsilateral kidney; molecular testing of 8 of the latter showed wild-type KRAS gene despite the presence of KRAS mutations in 5 concurrent PRNRP. On follow up, no adverse pathologic events were seen (range 1-160 months; mean 44 months). In conclusion, the presence of KRAS mutations in small, clinically undetected PRNRP provides a unique finding to this entity and supports its being an early event in the development of these neoplasms.

Molecular analysis of adenocarcinomas of the rete testis demonstrates frequent alterations in genes involved in cell cycle regulation.

Adenocarcinomas of the rete testis (ACRT) are rare and aggressive testicular neoplasms that present predominantly in older men and have a tendency for early systemic spread. Their morphology spans a wide spectrum, including tumors with glandular, solid, papillary, micropapillary, glomeruloid, cribriform, and sarcomatoid growth patterns, or a combination thereof. The genomic alterations associated with these tumors have not been studied previously. We assessed eight ACRT published in prior clinicopathologic series using a solid tumor DNA sequencing panel. Pathogenic variants were identified in 6/8 cases. More specifically, four cases demonstrated inactivation of genes involved in cell cycle regulation, including CDKN2A, BAP1, TP53, and RB1. CDKN2A was the only recurrently affected gene, with pathogenic variants detected in 3/8 cases. One of these three cases had molecular evidence of concurrent homozygous (i.e. biallelic) NF2 inactivation by a frameshift variant and loss of the wildtype copy of the gene. One case had an internal tandem duplication in AKT, which has been previously described in juvenile granulosa cell tumor and sclerosing pneumocytoma and results in downstream activation of PI3K signaling. The remaining case with positive molecular findings harbored two concurrent truncating SETD2 variants. Multiple arm-level and chromosome-level copy number events were present in 3/8 cases, all of which harbored variants in genes involved in cell cycle regulation. In summary, ACRT are rare tumors with frequent inactivation of genes that play a major role cell cycle regulation, and a subset harbors variants that are potentially amenable to targeted therapy.

Merlin immunohistochemistry is useful in diagnosis of tumours within the spectrum of biphasic hyalinizing psammomatous renal cell carcinoma.

AIMS: Biphasic hyalinizing psammomatous (BHP) renal cell carcinoma (RCC) is a newly described emerging entity within the spectrum of papillary RCC in the WHO 2022 classification. Molecular analyses have discovered that BHP RCC consistently harbour somatic mutations in the neurofibromin 2 (NF2) gene. The NF2 gene product, merlin, is known to primarily function as a tumour suppressor. Merlin protein loss correlates closely with the presence of NF2 mutations in benign and malignant tumours arising in different sites. In the present study we explored the role of merlin immunohistochemistry (IHC) in tumours within the spectrum of BHP RCC to determine the diagnostic utility of this marker. MATERIALS AND METHODS: We performed merlin IHC in 13 BHP RCC, 18 papillary RCC, 10 TFE3-translocation RCC, 15 TFEB-altered RCC (including 13 TFEB-rearranged and 2 TFEB-amplified), and 10 mucinous tubular and spindle cell carcinomas of unknown mutational status. RESULTS: Unequivocal loss of merlin expression in >90% of the tumour cells was observed in 12/13 BHP-RCC (92%), with the remaining tumour demonstrating weak focal cytoplasmic expression in ~10% of the tumour. In contrast, merlin was diffusely or multifocally expressed in all papillary RCC, TFE3-translocation RCC, and TFEB-altered RCC, as well as in 70% of mucinous tubular and spindle carcinomas. CONCLUSIONS: In this study, merlin IHC was ~92% sensitive and ~94% specific for BHP RCC. These data suggest that merlin IHC is a reliable surrogate marker for the presence of underlying NF2 gene inactivation, being diagnostically useful to identify BHP RCC. CONCLUSIONS: In this study, merlin IHC was ~92% sensitive and ~94% specific for BHP RCC. These data suggest that merlin IHC is a reliable surrogate marker for the presence of underlying NF2 gene inactivation, being diagnostically useful to identify BHP RCC.

Large cell calcifying Sertoli cell tumour: a contemporary multi-institutional case series highlighting the diagnostic utility of PRKAR1A immunohistochemistry.

AIMS: Large cell calcifying Sertoli cell tumour (LCCSCT) is a rare testicular sex cord-stromal tumour that primarily affects young patients and is associated with Carney complex. We sought to characterise the clinicopathological features of a series of LCCSCT and evaluate the diagnostic utility of PRKAR1A immunohistochemistry (IHC). METHODS AND RESULTS: The LCCSCT cohort (n = 15) had a median age of 16 years (range = 2-30 years). Four patients were known to have Carney complex. PRKAR1A IHC was performed in each case. For comparison, PRKAR1A IHC was also assessed in other sex cord-stromal tumours, including Sertoli cell tumour, not otherwise specified (SCT, NOS; n = 10), intratubular large cell hyalinising Sertoli cell tumour (n = 1) and Leydig cell tumour (n = 23). Loss of cytoplasmic PRKAR1A expression was observed in all but one LCCSCT (14 of 15; 93%). PRKAR1A expression was retained in all SCTs, NOS (10 of 10; 100%), the majority of Leydig cell tumours (22 of 23; 96%) and an intratubular large cell hyalinising Sertoli cell tumour (1 of 1; 100%). One Leydig cell tumour showed equivocal staining (multifocal weak expression). CONCLUSIONS: Overall, PRKAR1A loss is both sensitive (93%) and highly specific (97%) for the diagnosis of LCCSCT. PRKAR1A loss may aid its diagnosis, particularly in sporadic cases and those that are the first presentation of Carney complex.

Eosinophilic Esophagitis Symptom Scores Are High in Children Without Eosinophilic Disease.

OBJECTIVES: The Pediatric Eosinophilic Esophagitis (EoE) Symptom Score version 2 (PEESSv2.0) is an EoE-specific validated metric for disease monitoring, but its use has not been explored outside of EoE. Our aim was to determine if PEESSv2.0 scores differentiate between children with EoE and non-EoE esophageal dysfunction undergoing initial esophagogastroduodenoscopy (EGD). METHODS: A prospective cohort study of pediatric subjects was conducted. Children ages 1-18 undergoing initial EGD for esophageal dysfunction were enrolled. Demographics, clinical history, and child self-report and parent-proxy report PEESSv2.0 symptom scores were collected at the time of EGD. Esophageal biopsies were reviewed, and EoE was defined as >15 eosinophils/high powered field (hpf) seen in any level of the esophagus. Non-EoE was defined as <15 eosinophils/hpf. RESULTS: Seventy-one children were included in the study from 2015 to 2018 [59% (42/71) males; mean age 9.2 years; range 1-17 years]. Fifty-eight percent (41/71) met criteria for EoE, and 42% (30/71) were labeled non-EoE. Non-EoE children and their parents had higher/worse median PEESSv2.0 total scores than those with EoE [47.0 vs 28.0 (P = 0.001) and 40.5 vs 26.5 (P = 0.012), respectively]. Non-EoE children reported higher median GERD [9.0 vs 4.0 (P = 0.003)], nausea/vomiting [9.0 vs 4.0 (P = 0.003)], and pain [11.0 vs 6.0 (P = 0.001)] subdomain scores compared to those with EoE. PEESSv2.0 dysphagia subdomain scores (child and parent-proxy) did not differ between EoE and non-EoE groups [22.0 vs 15.0 (P = 0.184) and 18.5 vs 17.4 (P = 0.330), respectively]. DISCUSSION: Total PEESSv2.0 scores were worse in non-EoE group compared to EoE group. Although PEESSv2.0 is validated for use in monitoring EoE therapy, it does not distinguish children with EoE from non-EoE esophageal dysfunction at the time of diagnostic EGD.

Comparative molecular analysis of testicular Leydig cell tumors demonstrates distinct subsets of neoplasms with aggressive histopathologic features.

Testicular Leydig cell tumor (LCT), the most common sex-cord stromal tumor in men, represents a small fraction of all testicular tumors (~1 to 3%). Although most testicular LCTs are indolent and cured by radical orchiectomy, 5-10% have aggressive biology and metastatic potential. In primary LCTs, large size, cytologic atypia, necrosis, increased mitotic activity, and vascular invasion have been associated with clinically aggressive tumors. From a molecular perspective, the characteristics of aggressive LCTs and the differences between aggressive and nonaggressive LCTs remain largely unexplored. This study compares the genomic landscape of aggressive and nonaggressive testicular LCTs. Twenty-six cases were analyzed using next-generation DNA sequencing (NGS) and immunohistochemistry. Cases were classified as aggressive LCT if they met published criteria for malignancy in primary (i.e., testicular) tumors or if they had pathology-proven metastatic disease; otherwise, cases were considered nonaggressive. This multi-institutional series included 18 aggressive LCTs (14 primary/testicular, 4 metastatic) and 8 nonaggressive LCTs. Two cases (2/26, 8%; both aggressive LCTs) failed sequencing and had negative (i.e., uninformative) FH immunohistochemistry results. One additional primary aggressive LCT failed sequencing but had informative FH immunohistochemistry results. Combined NGS and immunohistochemical analysis demonstrated FH inactivation in 5/26 cases (19%). In addition, NGS demonstrated CTNNB1 mutations or biallelic APC inactivation in 9/23 cases (39%), copy number changes without recurrent mutations in 6/23 (26%) cases, and no alterations in 4/23 cases (17%). CTNNB1 mutations were present in both aggressive and nonaggressive LCTs. In contrast, FH inactivation and multiple copy number changes were only identified in aggressive LCTs. In conclusion, three distinct subgroups of aggressive LCTs were characterized by FH inactivation, Wnt pathway activation, and copy number changes without recurrent mutations, respectively. Nuclear translocation of ß-catenin and Wnt pathway activation appear to be early driver events that provide an environment conducive for progression to aggressive biology in a subset of LCTs.

EWSR1-PATZ1 fusion renal cell carcinoma: a recurrent gene fusion characterizing thyroid-like follicular renal cell carcinoma.

Thyroid-like follicular renal cell carcinoma is an uncommon kidney tumor with no distinct molecular alteration described to date. This cohort of eight women with mean and median ages of 45 and 46 years, respectively (range 19-65 years), had unencapsulated, well-circumscribed tumors composed of tightly packed anastomosing follicle-like cysts filled with eosinophilic colloid-like material and lined by cuboidal cells with high nuclear to cytoplasmic ratios, oval to elongated nuclei with perpendicular arrangement toward the lumens, and prominent nuclear overlapping. The stroma between these was minimal with the exception of two tumors. Calcifications and necrosis were absent. Immunohistochemically, the tumors were positive for KRT19 (7/7), PAX8 (5/5), cyclin D1 (6/6), KRT7 (5/7), and AMACR (1/5; focal, weak), and were negative for WT1, TTF1 (transcription termination factor-1), and thyroglobulin. In three of three tumors tested molecularly, EWSR1-PATZ1 fusion was identified by RNA sequencing and confirmed by RT-PCR and Sanger sequencing. Over a follow-up period of 1-7 years, no evidence of recurrence or metastasis has been detected. The EWSR1-PATZ1 fusion has been recognized as a recurrent alteration in a subset of round to spindle cell sarcomas with EWSR1-non-ETS fusions (EWSR1-PATZ1 sarcoma) and in several central nervous system tumors. The finding of an EWSR1-PATZ1 fusion in all three of the thyroid-like follicular renal cell carcinomas for which sufficient tissue was available for genomic profiling provides the first distinct molecular abnormality in thyroid-like follicular renal cell carcinomas, supporting its designation as a distinct diagnostic entity.

Testicular Tumors: A Contemporary Update on Morphologic, Immunohistochemical and Molecular Features.

Testicular tumors are incredibly diverse and one of the most challenging areas in surgical pathology. Because of the rarity and overlapping features with numerous entities occurring in the testis and paratestis, these tumors pose a diagnostic challenge even to the most experienced general pathologists. In 2016, the latest "World Health Organization (WHO) classification of testicular tumors" was released, which incorporated several updates to the previous 2004 classification system. These updates involved several entities, including germ cell tumors, sex cord-stromal tumors, tumors containing both germ cells and sex-cord stromal cells, a miscellaneous group of testicular tumors and paratesticular tumors. In addition, significant changes were also introduced in the 2018 AJCC TNM staging (8th edition) regarding testicular tumors. The germ cell tumors are divided into 2 major groups; tumors derived from germ cell neoplasia in situ (GCNIS) and those unrelated to GCNIS. The GCNIS associated tumors include seminomatous and nonseminomatous germ cell tumors, which constitute a heterogeneous group of tumors. Non-GCNIS-associated tumors include prepubertal-type teratoma, prepubertal yolk sac tumor, mixed prepubertal-type teratoma and yolk sac tumor and spermatocytic seminoma. In the sex cord-stromal category, the tumors are classified based on their cells of origin. Most are Leydig cell tumors and Sertoli cell tumors; however, several mixed and diverse entities based on cell types are included in this group. Gonadoblastoma is the only tumor in the mixed germ cell and sex cord-stromal tumor category. Because of recent advances in molecular techniques, abundant new genetic information has emerged which helped classify the tumors based on the molecular alterations and provided insights into the tumor pathogenesis. This review focused on the updates related to testicular germ cell tumors and sex cord-stromal tumors and described the morphologic, immunohistochemical and molecular characteristics with an aim to provide a practical diagnostic approach and an update on relevant recent molecular advances.