Comprehensive clinicopathological, molecular, and methylation analysis of mesenchymal tumors with NTRK and other kinase gene aberrations.

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.

Spindle cell rhabdomyosarcomas: With TFCP2 rearrangements, and novel EWSR1::ZBTB41 and PLOD2::RBM6 gene fusions. A study of five cases and review of the literature.

AIMS: Spindle-cell/sclerosing rhabdomyosarcomas (SS-RMS) are clinically and genetically heterogeneous. They include three well-defined molecular subtypes, of which those with EWSR1/FUS::TFCP2 rearrangements were described only recently. This study aimed to evaluate five new cases of SS-RMS and to perform a clinicopathological and statistical analysis of all TFCP2-rearranged SS-RMS described in the English literature to more comprehensively characterize this rare tumour type. METHODS AND RESULTS: Cases were retrospectively selected and studied by immunohistochemistry, fluorescence in situ hybridization with EWSR1/FUS and TFCP2 break-apart probes, next-generation sequencing (Archer FusionPlex Sarcoma kit and TruSight RNA Pan-Cancer Panel). The PubMed database was searched for relevant peer-reviewed English reports. Five cases of SS-RMS were found. Three cases were TFCP2 rearranged SS-RMS, having FUSex6::TFCP2ex2 gene fusion in two cases and triple gene fusion EWSR1ex5::TFCP2ex2, VAX2ex2::ALKex2 and VAX2intron2::ALKex2 in one case. Two cases showed rhabdomyoblastic differentiation and spindle-round cell/sclerosing morphology, but were characterized by novel genetic fusions including EWSR1ex8::ZBTB41ex7 and PLOD2ex8::RBM6ex7, respectively. In the statistical analysis of all published cases, CDKN2A or ALK alterations, the use of standard chemotherapy and age at presentation in the range of 18-24 years were negatively correlated to overall survival. CONCLUSION: EWSR1/FUS::TFCP2-rearranged SS-RMS is a rare rhabdomyosarcoma subtype, affecting predominantly young adults with average age at presentation 34 years (median 29.5 years; age range 7-86 years), with a predilection for craniofacial bones, rapid clinical course with frequent bone and lung metastases, and poor prognosis (3-year overall survival rate 28%).

Neuroendocrine Marker Expression in Primary Non-neuroendocrine Epithelial Tumors of the Ovary: A Study of 551 Cases.

Expression of neuroendocrine (NE) markers in primary ovarian non-NE epithelial tumors has rarely been evaluated. The aim of our study was to evaluate the expression of the most widely used NE markers in these neoplasms and to determine any prognostic significance of NE marker expression. The cohort consisted of 551 primary ovarian tumors, including serous borderline tumors, low-grade serous carcinomas, high-grade serous carcinomas (HGSC), clear cell carcinomas, endometroid carcinomas, mucinous borderline tumors, and mucinous carcinomas. Immunohistochemical analysis was performed using antibodies against INSM1, synaptophysin, chromogranin, and CD56 on tissue microarray. Positivity for INSM1, synaptophysin, chromogranin, and CD56 was most frequently observed in mucinous tumors (48.7%, 26.0%, 41.5%, and 100%, respectively). The positivity for these NE markers was mostly restricted to nonmucinous elements distributed throughout the tumor. The mucinous borderline tumor and mucinous carcinomas groups had similar proportions of positivity (mucinous borderline tumor: 53%, mucinous carcinomas: 39%). In the other tumor types, except for HGSC, there was only focal expression (5%-10%) or negativity for NE markers. HGSC showed high CD56 expression (in 26% of cases). Survival analysis was only performed for CD56 in HGSC as this was the only group with sufficient positive cases, and it showed no prognostic significance. Except for mucinous tumors, expression of NE markers in non-NE ovarian epithelial tumors is low. CD56 expression in HGSC occurs frequently but is without diagnostic or prognostic value.

TFG::MET-rearranged soft tissue tumor: A rare infantile neoplasm with a distinct low-grade triphasic morphology.

This article presents 2 cases of TFG::MET-rearranged mesenchymal tumor, an extremely rare molecular subset among an emerging group of mesenchymal neoplasms with kinase gene (NTRK, BRAF, RET and others) alterations. Both tumors were congenital, occurred in female patients and presented as huge masses on the trunk and thigh, measuring 18 and 20 cm in the largest dimension. Both cases showed identical areas with a distinctive triphasic morphology resembling fibrous hamartoma of infancy (FHI), consisting of haphazardly arranged ovoid to spindled cells traversed by variably cellular and hyalinized fascicles admixed with (most likely non-neoplastic) adipose tissue. In other areas, a high-grade infantile fibrosarcoma/malignant peripheral nerve sheath tumor-like (IFS/MPNST-like) morphology was present in both cases. While the first case co-expressed CD34 and S100 protein, the other case did not. When combined with the three previously reported MET-rearranged cases (of which two harbored TFG::MET fusion), 3/5 and 3/4 of MET-rearranged and TFG::MET fusion-associated tumors, respectively exhibited similar triphasic FHI-like low-grade morphology. This points toward the existence of a relatively distinct morphological subset among kinase-fusion-associated tumors which seems to be strongly associated with MET fusions. It seems some of these low-grade cases may transform into a high-grade variant with IFS/MPNST-like morphology as has been observed in other tumors with kinase gene fusions. While most cases seem to follow an indolent clinical course, the recognition of these tumors is clinically relevant as MET tyrosine kinase inhibitors might represent an effective treatment option for clinically aggressive or unresectable cases.

Primary Mucinous Tumors of the Ovary: An Interobserver Reproducibility and Detailed Molecular Study Reveals Significant Overlap Between Diagnostic Categories.

Primary ovarian mucinous tumors represent a heterogeneous group of neoplasms, and their diagnosis may be challenging. We analyzed 124 primary ovarian mucinous tumors originally diagnosed as mucinous borderline tumors (MBTs) or mucinous carcinomas (MCs), with an emphasis on interobserver diagnostic agreement and the potential for diagnostic support by molecular profiling using a next-generation sequencing targeted panel of 727 DNA and 147 RNA genes. Fourteen experienced pathologists independently assigned a diagnosis from preset options, based on a review of a single digitized slide from each tumor. After excluding 1 outlier participant, there was a moderate agreement in diagnosing the 124 cases when divided into 3 categories (κ = 0.524, for mucinous cystadenoma vs MBT vs MC). A perfect agreement for the distinction between mucinous cystadenoma/MBT as a combined category and MC was found in only 36.3% of the cases. Differentiating between MBTs and MCs with expansile invasion was particularly problematic. After a reclassification of the tumors into near-consensus diagnostic categories on the basis of the initial participant results, a comparison of molecular findings between the MBT and MC groups did not show major and unequivocal differences between MBTs and MCs or between MCs with expansile vs infiltrative pattern of invasion. In contrast, HER2 overexpression or amplification was found only in 5.3% of MBTs and in 35.3% of all MCs and in 45% of MCs with expansile invasion. Overall, HER2 alterations, including mutations, were found in 42.2% of MCs. KRAS mutations were found in 65.5% and PIK3CA mutations in 6% of MCs. In summary, although the diagnostic criteria are well-described, diagnostic agreement among our large group of experienced gynecologic pathologists was only moderate. Diagnostic categories showed a molecular overlap. Nonetheless, molecular profiling may prove to be therapeutically beneficial in advanced-stage, recurrent, or metastatic MCs.

BDNF, sHLA-G, and sTREM-1 are useful blood biomarkers for identifying grade IV glioma patients.

Inflammation and immunity belong to the main factors influencing tumor growth. In this study, we attempted to identify a profile of biomarkers associated with gliomas. We found decreased serum levels of sTREM-1 (soluble triggering receptor expressed on myelocytes) and increased levels of IL-10 in all grades of glioma patients in comparison with healthy controls (sTREM-1: grade II: p=0.0051, grade III: p=0.02, grade IV: p=0.01; IL-10: grade II: p=0.0017, grade III: p=0.03, grade IV: p=0.007). However, we did not find any combination of tested markers with good sensitivity and specificity in grades II and III of glioma patients to discriminate them from healthy controls. In grade IV glioma patients, two sets of markers showed promising results in distinguishing patients from healthy people. For the first set consisting of four selected markers, sTREM-1, sHLA-G, BDNF, and IL-13, the ROC curves indicate a good discriminatory capability for glioblastoma patients (AUC=0.9510). The best discriminatory capability for glioblastoma patients (AUC=0.9534) was found for the second set consisting of three selected markers sTREM-1, sHLA-G, and BDNF with 79.2% sensitivity and 94.1% specificity.

HLA-G 5'URR regulatory polymorphisms are associated with the risk of developing gliomas.

BACKGROUND: Human leukocyte antigen G (HLA-G) belongs to non-classical MHC class I molecules that is involved in the suppression of immune response. As HLA-G plays important role in the maintenance of fetal tolerance, its overexpression has been associated with tumor progression. For the regulation of HLA-G levels, genetic variants within the 5' upstream regulatory region (5'URR) are of crucial importance. Our study aimed to analyze the association between 16 HLA-G 5'URR variants, sHLA-G level and clinical variables in glioma patients. METHODS: We investigated 59 patients with gliomas (mean age 54.70 ± 15.10 years) and 131 healthy controls (mean age 41.45 ± 9.75 years). Patient's blood was obtained on the day of surgical treatment. The HLA-G 5'URR polymorphisms were typed by direct sequencing and the plasma level of sHLA-G assessed by ELISA. RESULTS: Haploblock within HLA-G 5'URR consisting of -762T, -716G, -689G, -666T, -633A, followed by -486C and -201A alleles were significantly more frequent in patients with gliomas than in the controls (p < 0.05). No correlation of HLA-G 5'URR variants with sHLA-G plasma level was found. Analysis of HLA-G 5'URR variants with main clinical variables in patients with grade IV gliomas revealed that haploblock carriers of -762CT, -716TG, -689AG, -666GT, -633GA, -486AC, -477GC, -201GA followed by -369AC carriers tend to have lower age at onset as compared to other genotype carriers (p = 0.04). CONCLUSION: Our results suggest genetic association of HLA-G 5'URR variants with risk of developing gliomas and possible contribution of HLA-G to disease pathology.

Pattern-based approach to duodenitis and duodenopathy.

Duodenum is currently the most popular site to obtain samples of intestinal mucosa for recognition of a disorder leading to malabsorption. Although there are significant overlaps between histological findings described in various non-neoplastic diseases of the duodenum, recognition of one of the six basic morphologic patterns, namely coeliac disease-like pattern, active chronic duodenitis, acute GvHD-like pattern, enteritis with predominant eosinophilic infiltration, enteritis with predominant infiltration by macrophages, and non-inflammatory enteropathy, usually allows diagnostic separation, especially if subtle histological details, clinical setting and serological investigation are taken into account.

Pattern-based approach to gastritis and gastropathy.

Histological investigation of non-neoplastic endoscopic biopsies of gastric mucosa is one of the most common tasks most pathologists have to face on daily basis. Although the most common clinical question is still being whether Helicobacter organisms are found, pathologists have to bear in mind the whole spectrum of causes and associated morphological patterns of gastritides and gastropathies, governed by characteristic combinations of various types of inflammatory infiltrate, alterative and reactive changes of epithelial component, vascular response, and variability of stromal composition. The association of histopathologic pattern with supposed etiology can be sometimes proved by direct detection of the cause of morphologic changes in the investigated endoscopic sample.

News in WHO 2021 classification of tumours of the central nervous system.

The aim of the presented communication is to clearly inform the general professional public about the newly approved modifications in this classification, including the newly approved types of tumours. A significant change is the new grading system for these tumours, including the innovative involvement of tumour profiling at the molecular level in the system for determining the degree of tumour differentiation and the application of the principle of integrated diagnostics, i. e. the synthesis of available histopathological and molecular findings in CNS tumors.

EWSR1-PATZ1-rearranged sarcoma: a report of nine cases of spindle and round cell neoplasms with predilection for thoracoabdominal soft tissues and frequent expression of neural and skeletal muscle markers.

The knowledge of clinical features and, particularly, histopathological spectrum of EWSR1-PATZ1-rearranged spindle and round cell sarcomas (EPS) remains limited. For this reason, we report the largest clinicopathological study of EPS to date. Nine cases were collected, consisting of four males and five females ranging in age from 10 to 81 years (average: 49 years). Five tumors occurred in abdominal wall soft tissues, three in the thorax, and one in the back of the neck. Tumor sizes ranged from 2.5 to 18 cm (average 6.6 cm). Five patients had follow-up with an average of 38 months (range: 18-60 months). Two patients had no recurrence or metastasis 19 months after diagnosis. Four patients developed multifocal pleural or pulmonary metastasis and were treated variably by surgery, radiotherapy, and chemotherapy. The latter seemed to have little to no clinical benefit. One of the four patients was free of disease 60 months after diagnosis, two patients were alive with disease at 18 and 60 months, respectively. Morphologically, low, intermediate, and high-grade sarcomas composed of a variable mixture of spindled, ovoid, epithelioid, and round cells were seen. The architectural and stromal features also varied, resulting in a broad morphologic spectrum. Immunohistochemically, the following markers were most consistently expressed: S100-protein (7/9 cases), GFAP (7/8), MyoD1 (8/9), Pax-7 (4/5), desmin (7/9), and AE1/3 (4/9). By next-generation sequencing, all cases revealed EWSR1-PATZ1 gene fusion. In addition, 3/6 cases tested harbored CDKN2A deletion, while CDKN2B deletion and TP53 mutation were detected in one case each. Our findings confirm that EPS is a clinicopathologic entity, albeit with a broad morphologic spectrum. The uneventful outcome in some of our cases indicates that a subset of EPS might follow a more indolent clinical course than previously appreciated. Additional studies are needed to validate whether any morphological and/or molecular attributes have a prognostic impact.

Superficial CD34-positive fibroblastic tumor and PRDM10-rearranged soft tissue tumor are overlapping entities: a comprehensive study of 20 cases.

AIMS: Superficial CD34-positive fibroblastic tumor (SCD34FT) and PRDM10-rearranged soft tissue tumor (PRDM10-STT) are rare mesenchymal tumors. These lesions have clinicopathological similarities, but their relationship remains controversial. This study aimed to characterise a series of cases of SCD34FT and PRDM10-STT. METHODS AND RESULTS: Ten lesions each of SCD34FT and PRDM10-STT were studied using immunohistochemistry, array-comparative genomic hybridisation (aCGH), RNA sequencing and exome sequencing. Tumors mainly occurred in young adults, were generally small (< 5 cm) and arose predominantly in the superficial soft tissues of the lower extremities. Follow-up data were available in 15 cases (SCD34FT, n = 7, median 16 months; PRDM10-STT, n = 8, median 14 months), local recurrences occurred in four cases (SCD34FT, two of 10; PRDM10-STT, two of 10), while no distant spread was documented. Morphologically, tumors were relatively well-circumscribed and composed of sheets and fascicles of spindle and pleomorphic cells showing low mitotic activity (< 1/mm²) without necrosis. Other findings included: granular cell change, lipoblast-like cells, ectatic blood vessels with fibrinous material, myxoid stromal changes, metaplastic bone and increased mitotic activity (> 1/mm²). All tumors diffusely expressed CD34, while pan-keratin and desmin were commonly seen focally. SynCAM3 was diffusely expressed in 12 cases (SCD34FT, n = 5; PRDM10-STT, n = 7), independently of fusion status. aCGH profiles were 'flat' (PRDM10-STT, n = 4; SCD34FT, n = 2) and exome sequencing showed no recurrent pathogenic mutations (PRDM10-STT, n = 2; SCD34FT, n = 4). Overall, the only morphological features seen exclusively in PRDM10-STT were myxoid stromal changes (three of 10) and metaplastic bone (two of 10). CONCLUSION: We expand the current knowledge on PRDM10-STT and SCD34FT and provide additional evidence for considering them as overlapping entities.

Targeted next generation sequencing of MLH1-deficient, MLH1 promoter hypermethylated, and BRAF/RAS-wild-type colorectal adenocarcinomas is effective in detecting tumors with actionable oncogenic gene fusions.

Oncogenic gene fusions represent attractive targets for therapy of cancer. However, the frequency of actionable genomic rearrangements in colorectal cancer (CRC) is very low, and universal screening for these alterations seems to be impractical and costly. To address this problem, several large scale studies retrospectivelly showed that CRC with gene fusions are highly enriched in groups of tumors defined by MLH1 DNA mismatch repair protein deficiency (MLH1d), and hypermethylation of MLH1 promoter (MLH1ph), and/or the presence of microsatellite instability, and BRAF/KRAS wild-type status (BRAFwt/KRASwt). In this study, we used targeted next generation sequencing (NGS) to explore the occurence of potentially therapeutically targetable gene fusions in an unselected series of BRAFwt/KRASwt CRC cases that displayed MLH1d/MLH1ph. From the initially identified group of 173 MLH1d CRC cases, 141 cases (81.5%) displayed MLH1ph. BRAFwt/RASwt genotype was confirmed in 23 of 141 (~16%) of MLH1d/MLH1ph cases. Targeted NGS of these 23 cases identified oncogenic gene fusions in nine patients (39.1%; CI95: 20.5%-61.2%). Detected fusions involved NTRK (four cases), ALK (two cases), and BRAF genes (three cases). As a secondary outcome of NGS testing, we identified PIK3K-AKT-mTOR pathway alterations in two CRC cases, which displayed PIK3CA mutation. Altogether, 11 of 23 (~48%) MLH1d/MLH1ph/BRAFwt/RASwt tumors showed genetic alterations that could induce resistance to anti-EGFR therapy. Our study confirms that targeted NGS of MLH1d/MLH1ph and BRAFwt/RASwt CRCs could be a cost-effective strategy in detecting patients with potentially druggable oncogenic kinase fusions.

Molecular testing in endometrial carcinoma - joint recommendation of Czech Oncological Society, Oncogynecological Section of the Czech Gynecological and Obstetrical Society, Society of Radiation Oncology, Biology and Physics, and the Society of Czech Pathologists.

Molecular classification of endometrial carcinoma is becoming an important part of the dia-gnostic process with direct therapeutic implications. Recent international guidelines, including the joint recommendation of the European Society of Gynaecological Oncology, the European Society for Radiotherapy and Oncology and the European Society of Pathology include the molecular classification into standard dia-gnostic algorithms. Molecular testing of endometrial carcinomas is also recommended in the latest (5th edition) of the World Health Organization classification of female genital tumors. Due to the need to implement these recommendations in practice, representatives of four professional societies of the Czech Medical Association of J. E. Purkyně (the Czech Oncological Society, the Oncogynecological Section of the Czech Gynecological and Obstetrical Society, the Society of Radiation Oncology, Biology and Physics, and the Society of Czech Pathologists) organized a meeting focused on this topic. Recommendation for molecular testing of endometrial carcinoma in routine dia-gnostic practice in the Czech Republic.

Undiagnosed cryptococcal meningoencephalitis with extensive hypoxic-ischemic brain injury mimicking grade 3 diffuse axonal injury.

In this article, we report the autopsy findings of a 50-year-old immunocompetent woman, who was hospitalized with an altered state of consciousness. Examinations, including cerebrospinal fluid analysis, carried out during hospitalization failed to identify the infectious agent causing progressive loss of consciousness and quadriparesis. The patient died within 8 days of admission to the hospital. Post-mortem microscopic and culture examination revealed Cryptococcus species. Death was attributed to cryptococcal meningoencephalitis. Histologic examination revealed accumulation of cryptococcus mimicking erythrocytes and extensive hemorrhage in hematoxylin and eosin-stained sections of the brain. Multifocal obliteration of the vascular bed by yeast was accompanied by hypoxic-ischemic brain injury mimicking traumatic diffuse axonal injury.

Secondary pulmonary hypoplasia associated with calcified Meckel´s diverticulum with osseous metaplasia.

In this paper, we report autopsy findings of a 1-day old full-term mature female neonate with pulmonary hypoplasia diagnosed postnatally. Death was attributed to acute respiratory failure due to hyaline membrane disease. We describe pathological features of calcified Meckels diverticulum with osseous metaplasia and inflammatory changes in adjacent peritoneum. As far as we know, this case report documents the youngest patient ever diagnosed with calcified Meckels diverticulum with osseous metaplasia.

Molecular testing in endometrial carcinoma (Joint recommendation of Czech Oncological Society, Oncogynecological Section of the Czech Gynecological and Obstetrical Society, Society of Radiation Oncology, Biology and Physics, and the Society of Czech Pathologists).

Molecular classification of endometrial carcinoma is becoming an important part of the diagnostic process with direct therapeutic implications. Recent international guidelines, including the joint ESGO-ESTRO-ESP recommendation, include the molecular classification into standard diagnostic algorithms. Molecular testing of endometrial carcinomas is also recommended in the latest (5th) edition of the WHO classification of Female Genital Tumors. Due to the need to implement these recommendations in practice, representatives of four professional societies of Czech Medical Association of J. E. Purkyně (Czech Oncological Society, Oncogynecological Section of the Czech Gynecological and Obstetrical Society, Society of Radiation Oncology, Biology and Physics, and the Society of Czech Pathologists) organized a meeting focused on this topic. The result of this meeting is a joint recommendation for molecular testing of endometrial carcinoma in routine diagnostic practice in the Czech Republic.

Novel EIF5A-USP6 Gene Fusion in Nodular Fasciitis Associated With Unusual Pathologic Features: A Report of a Case and Review of the Literature.

Nodular fasciitis (NF) is a benign self-limiting soft tissue lesion that has long been considered a reactive process. Recently, however, the USP6 gene rearrangement has been discovered, and the neoplastic nature of this tumor was suggested. Since then, many fusion partners of the USP6 gene have been reported, with the MYH9 gene as the most common. In this article, we describe a case of NF with a novel EIF5A-USP6 gene fusion associated with unusual pathological features. A 41-year-old healthy woman with a painful, rapidly growing subcutaneous mass on the left forearm with a size of 0.8 cm is presented. A soft tissue fragment measuring 1 cm was surgically excised. Owing to positive surgical margins, re-excision was performed, yielding another 2-cm fragment. The lesion was extensively histologically investigated. Immunohistochemical and molecular-genetic analysis, namely fluorescence in situ hybridization, next-generation sequencing, and reverse transcriptase-polymerase chain reaction, were also performed. Histology revealed a dermally located, mitotically active myofibroblastic proliferation with myxoid areas that ulcerated the overlying epidermis. One atypical mitotic figure was also found. The lesion showed positive immunohistochemical staining with smooth muscle actin, whereas S100 protein and CD34 stains were negative. Using fluorescence in situ hybridization, the USP6 gene rearrangement was detected and subsequent analysis using the Archer fusionPlex Sarcoma kit revealed a novel EIF5A-USP6 gene fusion. In the appropriate clinicopathological context, the detection of USP6 gene rearrangement is extremely useful when diagnosing NF, significantly reducing the risk of misdiagnosis and inappropriate overtreatment.

S100 and CD34 positive spindle cell tumor with prominent perivascular hyalinization and a novel NCOA4-RET fusion.

We report a case of a 35-year old male patient with a tumor located in the deep dermis on his forearm. The lesion was completely excised but recurred 4 years later. The patient showed no signs of neurofibromatosis type 1. The morphology and immunophenotype of the tumor corresponded to the recently characterized group of soft tissue spindle cell lesions defined by a relatively uniform cytomorphology, patternless architecture, conspicuous stromal and perivascular hyalinization, S100 and CD34 coexpression and recurrent fusions involving RAF1, BRAF, and NTRK1/2 genes. Using a 592-gene panel and massively parallel next-generation sequencing platform, we initially detected only NF1 gene mutation in our case. However, further molecular testing with Archer fusion assay revealed a novel NCOA4-RET gene fusion, adding it to the list of multiple kinase fusions originally reported in these tumors. Although break-apart FISH showed false negative result due to the presence of intrachromosomal rearrangement, RT-PCR confirmed the fusion transcript. Knowing the exact fusion is of great clinical importance especially for patients within the aggressive subset of these neoplasms that could be treated with selective kinase inhibitors. The presented case underscores the benefits of massively parallel sequencing as the types and number of gene fusions these tumors can potentially harbor render single-gene assays such as FISH impractical, and in this particular case, also insensitive.

Immunohistochemistry in hollow urinary tract.

There is no ideal marker or established immunohistochemistry panel to confirm urothelial differentiation. Immunohistochemistry must be always indicated in concrete differential diagnostic consideration. In this review article, immunohistochemistry will be discussed in the three different settings - distinction of benign and malignant changes of urothelium, the most frequent pitfalls and non-urothelial neoplasms of urinary tract.