Infantile fibrosarcoma (IFS)/cellular congenital mesoblastic nephroma (cCMN) commonly harbors the classic ETV6-NTRK3 translocation. However, there are recent reports of mesenchymal tumors with IFS-like morphology harboring fusions of other receptor tyrosine kinases or downstream effectors, including NTRK1/2/3, MET, RET, and RAF1 fusions as well as one prior series with BRAF fusions. Discovery of these additional molecular drivers contributes to a more integrated diagnostic approach and presents important targets for therapy. Here we report the clinicopathologic and molecular features of 14 BRAF-altered tumors, of which 5 had BRAF point mutations and 10 harbored one or more BRAF fusions. Of the BRAF fusion-positive tumors, one harbored two BRAF fusions (FOXN3-BRAF, TRIP11-BRAF) and another harbored three unique alternative splice variants of EPB41L2-BRAF. Tumors occurred in ten males and four females, aged from birth to 32 years (median 6 months). Twelve were soft tissue based; two were visceral including one located in the kidney (cCMN). All neoplasms demonstrated ovoid to short spindle cells most frequently arranged haphazardly or in intersecting fascicles, often with collagenized stroma and a chronic inflammatory infiltrate. No specific immunophenotype was observed; expression of CD34, S100, and SMA was variable. To date, this is the largest cohort of BRAF-altered spindle cell neoplasms with IFS-like morphology, including not only seven novel BRAF fusion partners but also the first description of oncogenic BRAF point mutations in these tumors.

Alterations in kinase genes such as NTRK1/2/3 , RET , and BRAF underlie infantile fibrosarcoma (IFS), the emerging entity ‘ NTRK ‐rearranged spindle cell neoplasms’ included in the latest WHO classification, and a growing set of tumors with overlapping clinical and pathological features. In this study, we conducted a comprehensive clinicopathological and molecular analysis of 22 cases of IFS and other kinase gene‐altered spindle cell neoplasms affecting both pediatric and adult patients. Follow‐up periods for 16 patients ranged in length from 10 to 130 months (mean 38 months). Six patients were treated with targeted therapy, achieving a partial or complete response in five cases. Overall, three cases recurred and one metastasized. Eight patients were free of disease, five were alive with disease, and two patients died. All cases showed previously reported morphological patterns. Based on the cellularity and level of atypia, cases were divided into three morphological grade groups. S100 protein and CD34 were at least focally positive in 12/22 and 14/22 cases, respectively. Novel PWWP2A::RET , NUMA1::RET , ITSN1::RAF1 , and CAPZA2::MET fusions, which we report herein in mesenchymal tumors for the first time, were detected by RNA sequencing. Additionally, the first uterine case with BRAF and EGFR mutations and CD34 and S100 co‐expression is described. DNA sequencing performed in 13 cases uncovered very rare additional genetic aberrations. The CNV profiles showed that high‐grade tumors demonstrate a significantly higher percentage of copy number gains and losses across the genome compared with low‐ and intermediate‐grade tumors. Unsupervised clustering of the tumors’ methylation profiles revealed that in 8/9 cases, the methylation profiles clustered with the IFS methylation class, irrespective of their clinicopathological or molecular features. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Apoptosis plays an important role in the development and homeostasis of multicellular organisms and its deregulation may result in many serious diseases, including cancer. Now it is clear that some oncogenic mutations disrupt apoptosis, leading to tumour initiation, progression or metastasis. Here, expression of apoptotic genes in context of drug resistance was investigated. We examined total of 102 samples from leukemic patients (n = 60) and patients with solid tumours (n = 42). We used RT-PCR to determine the levels of mRNA expression and the in vitro chemoresistance of leukemic cells was evaluated using the MTT assay. We found statistically significant increase in mRNA expression of all investigated proteins (p53, BAX, Bcl-2 and Bcl-XL) between the leukemia samples and leukocytes from healthy volunteers. We did not find any significant difference in mRNA levels among the solid tumour samples. Notably, we showed a significant positive correlation in both leukemic and solid tumour patient groups between p53 and BAX mRNA. We found that the highest values for the Bcl-2/BAX ratio were in solid tumours in comparison to leukemic cells or normal leukocytes. Moreover, we assessed the impact of p53 and BAX mRNA levels on the sensitivity of the leukemic cells to selected cytostatics. Elevated levels of p53 and BAX mRNA may indicate cellular response to possible changes in genomic DNA integrity associated with malignant transformation. We suggest that the BAX gene is regulated by the p53 protein but the initiation of apoptosis through the transcription activation of BAX is blocked by the high levels of Bcl-2. Given that the apoptosis resistance mechanisms are different among oncological patients as well as stages of identical malignancy cases, personalized and specific combination therapy is proposed to be more effective in clinical application.

JAK2 mutations provide an objective major criterion for diagnosis of myeloproliferative neoplasms in the 2008 World Health Organization classification, and are particularly useful for cases of polycythemia vera (PV). High resolution melting analysis (HRM) using DNA from fresh samples for mutation detection in JAK2 exons 12 and 14 has been reported. Here, we describe two new HRM techniques that use both fresh and formalin-fixed paraffin-embedded marrow samples, allowing for both prospective and retrospective analyses. We used these novel assays to screen DNA isolated from paraffin-embedded marrow biopsies from 104 patients with PV for mutations. HRM mutation-positive samples were subsequently sequenced. Ninety-seven samples (93.3%) were positive solely for the JAK2 p.V617F. One harbored a 33 bp duplication in exon 12 along with an exon 14 p.V617F mutation, another had an exon 12 p.H538_K539delinsL, and a third carried a previously unreported mutation in PV, p.L611S, alone, and in cis with p.V617F. This indicates that these assays can detect known and novel JAK2 mutations in exons 12 and 14 using either fresh or paraffin-embedded archival materials.