Modern Pathology最新文献

A subset of perivascular epithelioid cell neoplasms (PEComas) is histologically malignant and at high risk for metastasis, and there is limited literature available on the genetic features of these lesions. In addition to driver alterations in the TSC/mTOR pathway or TFE3 fusions, recurrent ATRX mutations have been identified in malignant PEComas. ATRX mutations have been tightly associated with the Alternative Lengthening of Telomeres (ALT) phenotype in a variety of other tumor types. Whether malignant PEComas - regardless of ATRX mutational status - harbor the ALT phenotype has not been characterized. We conducted immunohistochemistry (IHC), next-generation sequencing (NGS), and telomere-specific fluorescence in situ hybridization (FISH) on a cohort of 32 malignant PEComas to evaluate for the ALT phenotype and to correlate with underlying genomic features. TSC1/2/mTOR/RICTOR mutations or TFE3 translocations were detected in 16/31 cases (52%) by NGS. Recurrent ATRX alterations were identified in 10 cases (32%). Sixteen cases underwent ALT FISH, 8 of which harbored ATRX alterations by NGS and/or ATRX loss by IHC, and 8 cases without detectable ATRX alterations by NGS or loss by IHC. 12 of these 16 cases demonstrated the ALT phenotype by FISH (75%). All 8 cases with ATRX mutations were ALT positive by FISH (100%). In 8 cases without ATRX alterations by NGS, 4 cases demonstrated ALT by FISH (50%). Of these 4 ALT-positive cases lacking ATRX genomic alterations, IHC revealed ATRX protein loss in 1 case. Overall, ATRX alterations were identified in 75% of ALT-positive tumors. Our study provides the first correlation between ALT and genomic features of malignant PEComas, demonstrating that ATRX alterations invariably predict ALT, but that a subset of tumors without mutations in known ALT suppressor genes also activate ALT. These findings confirm that the association between ATRX alterations and ALT observed in other tumor types applies to PEComas and indicate that in a subset of cases, ALT may be activated by ATRX independent mechanisms.

Vascular anomalies encompass a heterogeneous group of vascular tumors and malformations and are most often caused by singular somatic variants that arise in utero. The presence of multiple variants, including those in at least two different genes (multigenic variants), is rare in these mosaic disorders, and their contribution to histology and phenotype has not been well characterized. We present our molecular and histologic experience with multiple variants in a large cohort of individuals with vascular anomalies and other suspected somatic mosaic disorders. We performed a retrospective review of 1,299 individuals with suspected somatic mosaic disorders who were sequenced at our institution and identified 92 individuals (7%) with at least two clinically reportable variants. Our cohort includes eighteen individuals with multigenic variants with unknown phenotypic implications and thirteen individuals with well described multigenic variants with clear phenotypic significance. For many individuals, the multiple variants had clear clinical implications, including variants that may respond to targeted therapy (n=73) or germline variants (n=33) with surveillance implications for that individual and their immediate relatives. Provided clinical information and available H&E-stained slides (n=37) were reviewed, and lesions were classified according to established guidelines whenever possible. The majority of lesions had histologic features concordant with the observed genetic variants. However, four out of eighteen lesions with multigenic variants with unknown phenotypic implications had unique or unusual histologic features that did not fit into a specific diagnostic category. Our results demonstrate that broad sequencing of vascular anomalies, even in patients with known pathogenic variants, can be useful to identify additional clinically relevant variants which may refine diagnosis, respond to targeted therapy, or reveal a germline disorder that contributes to phenotype and may require increased surveillance.

Periductal stromal tumors of the breast (PDST) are rare biphasic neoplasms with morphologic similarities to phyllodes tumors (PT). The histologic spectrum of PDST is broad but has not been well-characterized, and their genetic underpinnings remain unknown. We profiled PDST by targeted next-generation sequencing (NGS) in correlation with their histomorphology, immunophenotype, and clinical characteristics (n=15). All patients were female, including 2 with Li-Fraumeni Syndrome, with a mean age of 48 years. Forty-two percent had synchronous or metachronous PT and/or fibroadenoma. Most PDST expressed CD34 (15/15), SMA (12/14), and at least focal nuclear HMGA2 (8/12) and/or beta-catenin (6/12). High-grade PDST (HGPDST, n=8) were defined by marked nuclear pleomorphism (8/8), and most had high (≥10 mitoses/10 HPF) and/or atypical mitotic activity (7/8) and pleomorphic multinucleated tumor cells (7/8). All HGPDST had p53 (88%, 7/8) and/or Rb/CDKN2A (75%, 6/8) alterations by NGS or immunohistochemistry. p53 aberrations correlated with the presence of pleomorphic multinucleated tumor cells. Both Li-Fraumeni Syndrome patients had HGPDST with loss-of-heterozygosity of the germline TP53 variant. Other altered genes in HGPDST included EGFR (25%, 2/8), NF1 (25%, 2/8), TERT promoter, PIK3CA, CDKN2A/B, LZTR1, KMT2B, and ARID2 (1 case each). Low-grade PDST (LGPDST), which lacked marked pleomorphism, high mitotic activity, or atypical mitoses (n=7), had simpler genomes than HGPDST and lacked bona fide cancer gene alterations, with TERT promoter mutation in 1 case. Copy number alterations in PDST overlapped with those reported in PT, including 13q loss in all HGPDST. Copy number profiling revealed shared clonality of synchronous LGPDST and PT in 1 patient. In summary, we describe herein the genetic landscape of PDST, demonstrate correlation of genetic features with high-grade versus low-grade histology, and identify TP53 among key oncogenic drivers of HGPDST, including in Li-Fraumeni Syndrome. The genetics of HGPDST overlap with borderline or malignant PT, consistent with their classification as PT variants that arise through a MED12-independent pathway.

Adenocarcinoma of the lung (LUAD) is common and highly lethal. Clinical grading of LUAD strongly predicts recurrence and survival after surgery and is determined by morphological assessment of histological growth patterns in resected tumors. In particular, the 2 archetypally lethal morphologies, solid, and micropapillary growth patterns, are highly distinct from each other, but little is known about their defining molecular features or how their appearances are related to their biology and mechanisms of lethality. Pure epithelial growth patterns and subregions were identified within 7 distinct LUAD growth patterns across 51 resected tumors and characterized using NanoString GeoMx digital spatial profiler in 160 epithelially pure regions of interest. Results were validated in 27 cases at the protein level using Akoya PhenoImager multiplex immunofluorescence, in 432 cases at the RNA level with TempO-Seq, and in 30 cases with an independent GeoMx digital spatial profiler. Analyses of gene expression reveal fundamental divergent evolutionary trajectories leading to solid and micropapillary growth. Additionally, we identify recurrent localized intratumoral plasticity in both growth patterns. These states can explain the origins of growth patterns and their mechanisms of virulence. Our work highlights dramatic divergence in gene expression programs between highly lethal modes of LUAD tumor growth. We go on to show how microscopically localized hypoxia in the primary tumor helps to establish and maintain cellular survival strategies and tumor architecture, suggesting morphology-specific mechanisms of LUAD tumor metastasis and suggesting new therapeutic vulnerabilities.

Follicular lymphoma (FL) patients have variable outcomes, underscoring the need for biomarkers for improved risk stratification. Current FL grading systems, based on subjective centroblast counts, suffer from poor reproducibility, despite evidence linking grade 3 FL to worse prognosis. We aimed to identify objective biomarkers for centroblasts and centrocytes to improve FL prognostication. We reanalyzed publicly available spatial and single-cell transcriptomic data from normal germinal centers (GCs) and FL samples. Reanalysis revealed distinct gene expression profiles: AICDA (AID) and CXCR4 highly expressed in GC dark zone cells (centroblasts), and CD40 and TFRC (CD71) in light zone cells (centrocytes). Single-cell RNA sequencing of FL samples further showed AID and CXCR4 overexpression in malignant Grade 3A cells and CD40 and CD71 in grade 1-2 cells. We validated these findings using immunohistochemistry (IHC) (single and multiplex) on tonsils and 59 FL specimens (42 Grade 1-2, 17 Grade 3). Grade 3 FL showed significantly higher expression of AID, CD71, and Ki67 compared to grade 1-2; with CXCR4 approaching significance. Receiver operating characteristic (ROC) curve analysis identified optimal cut-offs for AID (1.54%), CXCR4 (21.9%), Ki67 (21.6%), and CD71 (7.57%) to distinguish grade 3 from grade 1-2 FL, with AID showing the best discriminatory ability. Crucially, AID expression evaluation showed reproducibility across two different digital algorithms and two independent visual observers. Furthermore, we observed a trend toward shorter disease-specific survival (DSS) in patients with both FL grade 3 and high AID expression. This prognostic observation held true regardless of whether AID overexpression was assessed via digital evaluation (cut-off: 1.54%) or visual estimation (cut-off: 2%). In conclusion, AID, CXCR4, CD71, and Ki67 are promising biomarkers for objectively identifying FL grade 3, potentially enhancing the reproducibility of grading and serving as independent prognostic tools. Further clinical validation in uniformly treated FL cohorts is warranted.