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Results for “inflammatory myofibroblastic tumor”

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PubMed2026

Loss of Methylthioadenosine Phosphorylase (MTAP) Expression: A Potentially Useful Tool for Distinguishing Sarcomatoid Urothelial Carcinoma From Inflammatory Myofibroblastic Tumor.

Inflammatory myofibroblastic tumor (IMT) and sarcomatoid urothelial carcinoma (SarUC) can have striking histologic overlap but have significantly different prognoses and clinical management paradigms. Loss of methylthioadenosine phosphorylase (MTAP) protein expression by immunohistochemistry (IHC) serves as a useful surrogate for homozygous 9p21 deletion, a recurrent genomic alteration in urothelial carcinoma (UC). We analyzed MTAP expression by IHC in 65 SarUCs and 27 urinary tract IMTs to evaluate its utility in navigating this challenging differential diagnosis. Overall, MTAP loss was significantly more frequent in SarUC (55%) compared with IMT (4%) (P < .0001). Among 46 biphasic SarUCs with independently evaluable epithelial and mesenchymal components, divergent expression patterns were frequent. The most common pattern was retention of MTAP staining in both epithelial and mesenchymal components (19/46; 41% of cases), followed by selective retention of MTAP in the epithelial component and loss in the mesenchymal component (16/46; 35% of cases). MTAP loss was observed in both the epithelial and mesenchymal components in 11 out of 46 (24%) SarUC cases. None of the 46 biphasic SarUC cases showed selective MTAP loss in the epithelial component but retention in the mesenchymal component. MTAP IHC was also particularly valuable in assessing clonal relationships in 2 challenging biphasic cases in which the differential diagnosis included a collision between a noninvasive low-grade papillary UC and an IMT versus a subtle IMT-like SarUC arising in association with an overlying noninvasive low-grade papillary UC. Next-generation sequencing on a subset of cases (n = 11) was useful for confirming 9p deletion in cases with MTAP loss by IHC, and for demonstrating molecular hallmarks of urothelial neoplasia thereby providing additional diagnostic support for morphologically challenging SarUC cases with IMT-like morphology. Therefore, MTAP IHC can be useful in evaluating spindle cell lesions of the urinary tract, as loss is significantly more common in SarUC than in IMT, and enriched in the mesenchymal component of biphasic SarUC. However, MTAP loss can be seen in both entities, and the diagnosis of IMT-like spindle cell tumors in the urinary tract requires careful integration of morphologic, immunohistochemical, and molecular data.

Humans↗
PubMed2026

Pediatric intracranial inflammatory myofibroblastic tumor harboring DCTN1::ALK fusion: a case report with radiologic-pathologic-molecular correlation.

Central nervous system inflammatory myofibroblastic tumors are rare; pediatric DCTN1::ALK fusion cases are exceptionally uncommon. Here, we present an eight-year-old boy who presented with headache, vomiting, and a rapidly enlarging right frontal scalp mass. An MRI showed a dural, extra-axial lesion with mass effect. Histology confirmed IMT, and ALK immunohistochemistry was positive; next-generation sequencing (NGS) identified DCTN1 (exon 1-27)-ALK (exon 20-29) fusion, and FISH confirmed ALK rearrangement (33/100 nuclei). Genomic metrics showed tumor mutational burden (TMB) of 0.94/Mb, microsatellite stability, and CNV burden of 2.1%. He underwent near total resection followed by alectinib; to our knowledge, this is the first reported young pediatric (<10&#xa0;years old) CNS IMT with this fusion.

Humans↗
PubMed2026

Low-Grade Myofibroblastic Sarcoma Represents an Epigenetically Distinct Myofibroblastic Tumor With USP6 Upregulation and Stable Genome.

Low-grade myofibroblastic sarcoma (LGMS) is a rare, indolent mesenchymal neoplasm exhibiting myofibroblastic differentiation, with a propensity for local recurrence. The molecular basis of LGMS and its precise relationship with other histological mimics have remained largely undefined. To address this gap, we conducted the first comprehensive multiomics analysis of 6 LGMS cases, integrating whole-exome sequencing, RNA sequencing, and Illumina Methylation EPICv2 array profiling with comparative analysis against public sarcoma methylation cohorts and related fibroblastic tumors. Clinically, patients (median age 35.5 years) presented with small tumors (median size 1.45 cm), predominantly located in the head and neck, displaying classic histological features of diffusely infiltrative spindle cell fascicles with patchy mononuclear inflammation. Two of the 5 patients with follow-up developed local recurrence, and none metastasized (median follow-up duration 92.5 months). Genomically, all LGMS exhibited a low tumor mutational burden (median 2.31 mut/Mb) and a minimal fraction of genome altered, with TP53 and TSC2 deletions and NTRK1 and ERBB3 amplifications found in a subset of cases. No pathogenic fusions were detected. Transcriptomic profiling revealed a distinct signature featuring prominent USP6 overexpression and upregulation of inflammatory and immune-related genes, including CD274 (PD-L1), and enrichment of inflammatory and interferon-gamma response signatures. Epigenetically, LGMS formed a unique methylation cluster closest to inflammatory myofibroblastic tumor, with numerous differentially methylated regions and higher immune infiltration, particularly monocytes, compared with other fibroblastic tumors. These findings establish LGMS as a genomically stable, epigenetically distinct myofibroblastic sarcoma driven by USP6 overexpression and an inflammation-enriched transcriptome. They support its recognition as a standalone entity, facilitate integration into methylation-based sarcoma classifiers for improved diagnostic precision, and nominate USP6-associated pathways and immune checkpoint blockade as promising therapeutic strategies for recurrent or unresectable disease.

Humans↗
PubMed2026

An integrated single-cell and spatial transcriptomic atlas of thyroid cancer progression identifies prognostic fibroblast subpopulations.

Although well-differentiated thyroid carcinoma (WDTC) is characterized by a robust treatment response, aggressive subtypes, such as anaplastic thyroid carcinoma (ATC), remain highly lethal. To understand thyroid cancer evolution in both children and adults, we analyzed single-cell transcriptomes of 423,733 cells from 81 samples and spatially resolved key tumor and microenvironment populations across 28 tumors with spatial transcriptomics, including rare and unique composite WDTC/ATC tumors and pediatric diffuse sclerosing thyroid carcinomas. Additionally, we identified gene signatures of stromal cell populations in 5 large thyroid cancer bulk RNA-sequencing cohorts. Through this multi-institutional effort, we defined a population of POSTN+ myofibroblast cancer-associated fibroblasts (myCAFs) that are intimately associated with invasive tumor cells and correlate with poor prognosis, lymph node metastasis, and disease progression in thyroid carcinoma. We also revealed a population of inflammatory CAFs that are distant to tumor cells and are found in the inflammatory stromal microenvironment of autoimmune thyroiditis. Together, our study provides spatial profiling of thyroid cancer evolution in samples with mixed WDTC/ATC histopathology and identifies a prognostic myCAF subtype with potential clinical utility in predicting aggressive disease in both children and adults.

Humans↗