Prognostic Factors in Epithelioid Hemangioendothelioma: Analysis of a Nationwide Molecularly/Immunohistochemically Confirmed Cohort of 57 Cases.

Epithelioid hemangioendothelioma (EHE) is an extremely rare vascular sarcoma with variable aggressive clinical behavior. In this retrospective study, we aimed to investigate prognostic factors based on clinicopathologic findings in a molecularly/immunohistochemically confirmed nationwide multicenter cohort of 57 EHE cases. Patients had unifocal disease (n = 29), multifocal disease (n = 5), lymph node metastasis (n = 8) and/or distant metastasis (n = 15) at the time of diagnosis. The overall survival rate was 71.4% at 1 year and 50.7% at 5 years. Survival did not correlate with sex, age or histopathological parameters. No survival differences were observed between multifocal and metastatic disease, suggesting that multifocality represents early metastases and treatment options are limited in comparison to unifocal disease. In unifocal tumors, survival could be predicted using the risk stratification model of Shibayama et al., dividing the cases into low- (n = 4), intermediate- (n = 15) and high- (n = 3) risk groups. No clinical or histopathological parameters were associated with progressive unifocal disease course. Lymph node metastases at the time of diagnosis occurred in 14.0% of the cases and were mainly associated with tumor localization in the head and neck area, proposing lymph node dissection. In conclusion, our results demonstrate the aggressive behavior of EHE, emphasize the prognostic value of a previously described risk stratification model and may provide new insights regarding tumor focality, therapeutic strategies and prognosis.

Dynamic Contrast-enhanced and Diffusion-weighted Magnetic Resonance Imaging for Response Evaluation After Single-Dose Ablative Neoadjuvant Partial Breast Irradiation.

Purpose: We aimed to evaluate changes in dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) magnetic resonance imaging (MRI) scans acquired before and after single-dose ablative neoadjuvant partial breast irradiation (NA-PBI), and explore the relation between semiquantitative MRI parameters and radiologic and pathologic responses. Methods and Materials: We analyzed 3.0T DCE and DW-MRI of 36 patients with low-risk breast cancer who were treated with single-dose NA-PBI, followed by breast-conserving surgery 6 or 8 months later. MRI was acquired before NA-PBI and 1 week, 2, 4, and 6 months after NA-PBI. Breast radiologists assessed the radiologic response and breast pathologists scored the pathologic response after surgery. Patients were grouped as either pathologic responders or nonresponders (<10% vs ≥10% residual tumor cells). The semiquantitative MRI parameters evaluated were time to enhancement (TTE), 1-minute relative enhancement (RE1min), percentage of enhancing voxels (%EV), distribution of washout curve types, and apparent diffusion coefficient (ADC). Results: In general, the enhancement increased 1 week after NA-PBI (baseline vs 1 week median - TTE: 15s vs 10s; RE1min: 161% vs 197%; %EV: 47% vs 67%) and decreased from 2 months onward (6 months median - TTE: 25s; RE1min: 86%; %EV: 12%). Median ADC increased from 0.83 × 10-3 mm2/s at baseline to 1.28 × 10-3 mm2/s at 6 months. TTE, RE1min, and %EV showed the most potential to differentiate between radiologic responses, and TTE, RE1min, and ADC between pathologic responses. Conclusions: Semiquantitative analyses of DCE and DW-MRI showed changes in relative enhancement and ADC 1 week after NA-PBI, indicating acute inflammation, followed by changes indicating tumor regression from 2 to 6 months after radiation therapy. A relation between the MRI parameters and radiologic and pathologic responses could not be proven in this exploratory study.

EWSR1-The Most Common Rearranged Gene in Soft Tissue Lesions, Which Also Occurs in Different Bone Lesions: An Updated Review.

EWSR1 belongs to the FET family of RNA-binding proteins including also Fused in Sarcoma (FUS), and TATA-box binding protein Associated Factor 15 (TAF15). As consequence of the multifunctional role of EWSR1 leading to a high frequency of transcription of the chromosomal region where the gene is located, EWSR1 is exposed to aberrations such as rearrangements. Consecutive binding to other genes leads to chimeric proteins inducing oncogenesis. The other TET family members are homologous. With the advent of widely used modern molecular techniques during the last decades, it has become obvious that EWSR1 is involved in the development of diverse benign and malignant tumors with mesenchymal, neuroectodermal, and epithelial/myoepithelial features. As oncogenic transformation mediated by EWSR1-fusion proteins leads to such diverse tumor types, there must be a selection on the multipotent stem cell level. In this review, we will focus on the wide variety of soft tissue and bone entities, including benign and malignant lesions, harboring EWSR1 rearrangement. Fusion gene analysis is the diagnostic gold standard in most of these tumors. We present clinicopathologic, immunohistochemical, and molecular features and discuss differential diagnoses.

Myxoid pleomorphic liposarcoma-a clinicopathologic, immunohistochemical, molecular genetic and epigenetic study of 12 cases, suggesting a possible relationship with conventional pleomorphic liposarcoma.

Myxoid pleomorphic liposarcoma is a recently defined subtype of liposarcoma, which preferentially involves the mediastinum of young patients and shows mixed histological features of conventional myxoid liposarcoma and pleomorphic liposarcoma. While myxoid pleomorphic liposarcoma is known to lack the EWSR1/FUS-DDIT3 fusions characteristic of the former, additional genetic data are limited. To further understand this tumor type, we extensively examined a series of myxoid pleomorphic liposarcomas by fluorescence in situ hybridization (FISH), shallow whole genome sequencing (sWGS) and genome-wide DNA methylation profiling. The 12 tumors occurred in 6 females and 6 males, ranging from 17 to 58 years of age (mean 33 years, median 35 years), and were located in the mediastinum (n = 5), back, neck, cheek and leg, including thigh. Histologically, all cases consisted of relatively, bland, abundantly myxoid areas with a prominent capillary vasculature, admixed with much more cellular and less myxoid foci containing markedly pleomorphic spindled cells, numerous pleomorphic lipoblasts and elevated mitotic activity. Using sWGS, myxoid pleomorphic liposarcomas were found to have complex chromosomal alterations, including recurrent large chromosomal gains involving chromosomes 1, 6-8, 18-21 and losses involving chromosomes 13, 16 and 17. Losses in chromosome 13, in particular loss in 13q14 (including RB1, RCTB2, DLEU1, and ITM2B genes), were observed in 4 out of 8 cases analyzed. Additional FISH analyses confirmed the presence of a monoallelic RB1 deletion in 8/12 cases. Moreover, nuclear Rb expression was deficient in all studied cases. None showed DDIT3 gene rearrangement or MDM2 gene amplification. Using genome-wide DNA methylation profiling, myxoid pleomorphic liposarcomas and conventional pleomorphic liposarcomas formed a common methylation cluster, which segregated from conventional myxoid liposarcomas. While the morphologic, genetic and epigenetic characteristics of myxoid pleomorphic liposarcoma suggest a link with conventional pleomorphic liposarcoma, its distinctive clinical features support continued separate classification for the time being.

Loss of H3K27me3 occurs in a large subset of embryonal rhabdomyosarcomas: Immunohistochemical and molecular analysis of 25 cases.

Loss of histone 3 lysine 27 trimethylation (H3K27me3) has been described as a diagnostic marker for malignant peripheral nerve sheath tumor (MPNST), also discriminating MPNST with rhabdomyoblastic differentiation (malignant Triton tumor) from rhabdomyosarcoma (RMS). We studied the immunohistochemical expression of H3K27me3 in embryonal RMSs (ERMSs), performed methylation profiling in order to support the diagnosis and RNA-sequencing for comparison of the transcriptome of H3K27me3-positive and -negative cases. Of the 25 ERMS patients, 17 were males and 8 were females with an age range from 1 to 67 years (median, 6 years). None were known with neurofibromatosis type 1. One patient had Li-Fraumeni syndrome. Tumor localization included paratesticular (n = 9), genitourinary (n = 6), head/neck (n = 5), retroperitoneal (n = 4) and lower arm (n = 1). Five MPNSTs served as reference group. All ERMS had classical features including a variable spindle cell component. Immunohistochemical loss (partial or complete) of H3K27me3 was detected in 18/25 cases (72%). Based on methylation profiling, 22/22 cases were classified as ERMS. Using RNA sequencing, the ERMS group (n = 14) had a distinct gene expression profile in contrast to MPNSTs, confirming that the H3K27me3 negative ERMS cases do not represent malignant Triton tumors. When comparing H3K27me3-negative and -positive ERMSs, gene set enrichment analysis revealed differential expression of genes related to histone acetylation and normal muscle function with H3K27me3 negative ERMSs being associated with acetylation. Conclusion: Loss of H3K27me3 frequently occurs in ERMSs and correlates with H3K27 acetylation. H3K27me3 is not a suitable marker to differentiate ERMS (with spindle cell features) from malignant Triton tumor.

Tumor-Infiltrating Lymphocytes in Low-Risk Patients With Breast Cancer Treated With Single-Dose Preoperative Partial Breast Irradiation.

PURPOSE: Preoperative partial breast irradiation (PBI) has the potential to induce tumor regression. We evaluated the differences in the numbers of preirradiation tumor infiltrating lymphocytes (TILs) between responders and nonresponders after preoperative PBI in low-risk patients with breast cancer. Furthermore, we evaluated the change in number of TILs before and after irradiation. METHODS AND MATERIALS: In the prospective ABLATIVE study, low-risk patients with breast cancer underwent treatment with single-dose preoperative PBI (20 Gy) to the tumor and breast-conserving surgery after 6 or 8 months. In the preirradiation diagnostic biopsy and postirradiation resection specimen, numbers of TILs in 3 square regions of 450 × 450 µm were counted manually. TILs were visualized with CD3, CD4, and CD8 immunohistochemistry. Differences in numbers of preirradiation TILs between responders and nonresponders were tested using Mann-Whitney U test. Responders were defined as pathologic complete or near-complete response, and nonresponders were defined "as all other response." Changes in numbers of TILs after preoperative PBI was evaluated with the Wilcoxon signed rank test. RESULTS: Preirradiation tissue was available from 28 patients, postirradiation tissue from 29 patients, resulting in 22 pairs of preirradiation and postirradiation tissue. In these 35 patients, 15 had pathologic complete response (43%), 11 had a near-complete response (31%), 7 had a partial response (20%), and 2 had stable disease (6%). The median numbers of CD3+ TILs, CD4+ TILs, and CD8+ TILs in the preirradiation tumor tissue were 49 (interquartile range [IQR], 36-80), 45 (IQR, 28-57), and 19 (IQR, 8-35), respectively. The number of preirradiation TILs did not differ significantly between responders and nonresponders. The median numbers of CD3+ TILs, CD4+ TILs, and CD8+ TILs in postirradiation tumor tissue were 17 (IQR, 13-31), 26 (IQR, 16-35), and 7 (IQR, 5-11), respectively. CONCLUSIONS: After preoperative PBI in this limited cohort, the number of TILs in tumor tissue decreased. No differences in numbers of preirradiation TILs between responders and nonresponders were observed.

Single-cell derived tumor organoids display diversity in HLA class I peptide presentation.

Tumor heterogeneity is a major cause of therapeutic resistance. Immunotherapy may exploit alternative vulnerabilities of drug-resistant cells, where tumor-specific human leukocyte antigen (HLA) peptide ligands are promising leads to invoke targeted anti-tumor responses. Here, we investigate the variability in HLA class I peptide presentation between different clonal cells of the same colorectal cancer patient, using an organoid system. While clone-specific differences in HLA peptide presentation were observed, broad inter-clone variability was even more prevalent (15-25%). By coupling organoid proteomics and HLA peptide ligandomics, we also found that tumor-specific ligands from DNA damage control and tumor suppressor source proteins were prominently presented by tumor cells, coinciding likely with the silencing of such cytoprotective functions. Collectively, these data illustrate the heterogeneous HLA peptide presentation landscape even within one individual, and hint that a multi-peptide vaccination approach against highly conserved tumor suppressors may be a viable option in patients with low tumor-mutational burden.

USP6-Associated Neoplasms: A Rapidly Expanding Family of Lesions.

Nearly 20 years ago, the first description of a translocation involving chromosome 17 on which USP6 resides was described. Since then, not only the culprit gene but also many fusion partners, leading to transcriptional activation of USP6, have been detected. The first neoplasm known to harbor USP6 rearrangements was aneurysmal bone cyst. Since then, other entities like nodular fasciitis, myositis ossificans, fibro-osseous pseudotumor of digits, and a subgroup of fibromas of tendon sheath, probably representing tenosynovial nodular fasciitis, have been added to the list of USP6-rearranged lesions. Remarkably, all of them share clinical as well as morphological characteristics, and authors have suggested that these entities actually belong to the same spectrum. This review summarizes the current knowledge regarding USP6-rearranged lesions and further elaborates on how these neoplasms relate to one another. We propose to call these lesions UAN (Usp6-associated neoplasm).

Assessment of tumour proliferation by use of the mitotic activity index, and Ki67 and phosphohistone H3 expression, in early-stage luminal breast cancer.

AIMS: Phosphohistone H3 (PhH3) has been proposed as a novel proliferation marker in breast cancer. This study compares the interobserver agreement for assessment of the mitotic activity index (MAI), Ki67 expression, and PhH3 in a cohort of oestrogen receptor (ER)-positive breast cancer patients. METHODS AND RESULTS: Tumour samples of 159 luminal breast cancer patients were collected. MAI and PhH3 scores were assessed by three breast cancer pathologists. Ki67 scores were assessed separately by two of the three pathologists. PhH3-positive cells were counted in an area of 2 mm2 , with a threshold of ≥13 positive cells being used to discriminate between low-proliferative and high-proliferative tumours. Ki67 expression was assessed with the global scoring method. Ki67 percentages of <20% were considered to be low. The intraclass correlation coefficient (ICC) and Cohen's κ statistics were used to evaluate interobserver agreement. The impact on histological grading of replacing the MAI with PhH3 was assessed. Counting PhH3-positive cells was highly reproducible among all three observers (ICC of 0.86). The κ scores for the categorical PhH3 count (κ = 0.78, κ = 0.68, and κ = 0.80) reflected substantial agreement among all observers, whereas agreement for the MAI (κ = 0.38, κ = 0.52, and κ = 0.26) and Ki67 (κ = 0.55) was fair to moderate. When PhH3 was used to determine the histological grade, agreement in grading increased (PhH3, κ = 0.52, κ = 0.48, and κ = 0.52; MAI, κ = 0.43, κ = 0.35, and κ = 0.32), and the proportion of grade III tumours increased (14%, 18%, and 27%). CONCLUSION: PhH3 seems to outperform Ki67 and the MAI as a reproducible means to measure tumour proliferation in luminal-type breast cancer. Variation in the assessment of histological grade might be reduced by using PhH3, but would result in an increase in the proportion of high-grade cancers.

Kaposiform hemangioendothelioma and tufted angioma - (epi)genetic analysis including genome-wide methylation profiling.

Kaposiform hemangioendothelioma (KHE) is a locally aggressive vascular condition of childhood and is clinicopathologically related to tufted angioma (TA), a benign skin lesion. Due to their rarity molecular data are scarce. We investigated 7 KHE and 3 TA by comprehensive mutational analysis and genome-wide methylation profiling and compared the clustering, also with vascular malformations. Lesions were from 7 females and 3 males. The age range was 2 months to 9 years with a median of 10 months. KHEs arose in the soft tissue of the thigh (n = 2), retroperitoneum (n = 1), thoracal/abdominal (n = 1), supraclavicular (n = 1) and neck (n = 1). One patient presented with multiple lesions without further information. Two patients developed a Kasabach-Merritt phenomenon. TAs originated in the skin of the shoulder (n = 2) and nose/forehead (n = 1). Of the 5 KHEs and 2 TAs investigated by DNA sequencing, one TA showed a hot spot mutation in NRAS, and one KHE a mutation in RAD50. Unsupervised hierarchical clustering analysis indicated a common methylation pattern of KHEs and TAs, which separated from the homogeneous methylation pattern of vascular malformations. In conclusion, methylation profiling provides further evidence for KHEs and TAs potentially forming a spectrum of one entity. Using next generation sequencing, heterogeneous mutations were found in a subset of cases (2/7) without the presence of GNA14 mutations, previously reported in KHE and TA.

Tumor Response After Neoadjuvant Magnetic Resonance Guided Single Ablative Dose Partial Breast Irradiation.

PURPOSE: To assess the pathologic and radiologic response in patients with low-risk breast cancer treated with magnetic resonance (MR) guided neoadjuvant partial breast irradiation (NA-PBI) and to evaluate toxicity and patient-reported outcomes (PROs). METHODS AND MATERIALS: For this single-arm prospective trial, women with unifocal, non-lobular tumors with a maximum diameter of 20 mm (age, 50-70 years) or 30 mm (age, ≥70 years) and tumor-negative sentinel node(s) were eligible. Patients were treated with a single ablative dose of NA-PBI followed by breast-conserving surgery after an interval of 6 to 8 months. Target volumes were defined on radiation therapy planning computed tomography scan and additional magnetic resonance imaging. Prescribed doses to gross tumor volume and clinical target volume (gross tumor volume plus 20 mm margin) were 20 Gy and 15 Gy, respectively. Primary outcome was pathologic complete response (pCR). Secondary outcomes were radiologic response (on magnetic resonance imaging), toxicity (Common Terminology Criteria for Adverse Events), PROs (European Organisation for Research and Treatment of Cancer QLQ-BR23, Hospital Anxiety and Depression Scale), and cosmesis (assessed by patient, radiation oncologist, and BCCT.core software). RESULTS: Thirty-six patients were treated with NA-PBI, and pCR was reported in 15 patients (42%; 95% confidence interval, 26%-59%). Radiologic complete response was observed in 15 patients, 10 of whom had pCR (positive predictive value, 67%; 95% confidence interval, 39%-87%). After a median follow-up of 21 months (range, 12-41), all patients experienced grade 1 fibrosis in the treated breast volume. Transient grade 2 and 3 toxicity was observed in 31% and 3% of patients, respectively. Local recurrences were absent. No deterioration in PROs or cosmetic results was observed. CONCLUSIONS: NA-PBI has the potential to induce pCR in a substantial proportion of patients, with acceptable toxicity. This treatment seems a feasible alternative to standard postoperative irradiation and could even result in postponement or omission of surgery if pCR can be accurately predicted in selected low-risk patients.

A higher throughput and physiologically relevant two-compartmental human ex vivo intestinal tissue system for studying gastrointestinal processes.

A majority of the preclinical intestinal screening models do not properly reflect the complex physiology of the human intestinal tract, resulting in low translational value to the clinical situation. The often used cell lines such as Caco-2 or HT-29 are not well suited to investigate the different processes that predict oral bioavailability in real life, or processes involved in general gut health aspects. Therefore, highly realistic models resembling the human in vivo situation are needed; application of ex vivo intestinal tissue is an interesting and feasible alternative. After previously using porcine intestinal tissue as a predictive model for human intestinal absorption, we now have successfully applied human intestinal tissue into a newly developed InTESTine™ two-compartmental disposable device suitable for standard 6- or 24-well plate format. With this set-up we demonstrated (regional differences in) drug absorption, by using a subset of compounds with known varying Fa (fraction absorbed) values. A rank-order relationship of R2 = 0.85 could be established between the Fa and Papp of these commercially available drugs. Additionally, comparison between the InTESTine system and the established Ussing chamber technology showed a correlation of R2 = 0.94 (10 drugs) with respect to Papp values, indicating good comparison of both models. Besides absorption, intestinal wall metabolism of testosterone (CYP3A4) was determined by showing a linear formation (R2 = 0.99; up to 165 min) of the main metabolites androstenedione and 6Beta-hydroxytestosterone, indicating no loss of metabolic capacity of the intestinal tissue within the system. Enteroendocrine responses were assessed of the satiety hormones GLP-1 and PYY after stimulation with rebaudioside A and casein, resulting in significantly increased secretion to the luminal side as well as to the basolateral side. Incubation with the probiotic strain LGG showed to enhance the viability of the tissue by showing to decrease the LDH secretion compared to blank intestinal tissue. In conclusion, we show that human ex vivo intestinal tissue mounted in the higher throughput InTESTine 6- 24-transwell plate system is easy to handle and a suitable system to study diverse functional GI processes.

Calcifying fibrous tumor and inflammatory myofibroblastic tumor are epigenetically related: A comparative genome-wide methylation study.

Based on histological findings, calcifying fibrous tumor (CFT) may be a late (burned out) stage of inflammatory myofibroblastic tumor (IMT). This concept, however, has not been proven by molecular means. Five CFTs were analyzed for IMT-related rearrangements in ALK, ROS1 and RET using fluorescence in situ hybridization (FISH). Additionally, genome-wide methylation patterns were investigated and compared with IMT (n = 7), leiomyoma (n = 7), angioleiomyoma (n = 9), myopericytoma (n = 7) and reactive soft tissue lesions (n = 10) using unsupervised hierarchical cluster analysis and t distributed stochastic neighbor embedding. CFT patients, 4 females and 1 male, had a median age of 20 years ranging from 7 to 43 years. Two patients were younger than 18 years old. The tumors originated in the abdomen (n = 4) and axilla (n = 1). Histologically, all lesions were (multi) nodular and hypocellular consisting of bland looking (myo)fibroblasts embedded in a collagenous matrix with calcifications. FISH analysis brought up negative results for ALK, RET and ROS1 rearrangements. However, genome-wide methylation analysis revealed overlapping methylation patterns of CFT and IMT forming a distinct homogeneous methylation cluster with exception of one case clustering with myopericytoma/angioleiomyoma. In conclusion, DNA methylation profiling supports the concept that CFT and IMT represent both ends of a spectrum of one entity with CFT being the burn out stage of IMT.

"Fat-Rich" (Spindle Cell-Poor) Variant of Atypical Spindle Cell/Pleomorphic Lipomatous Tumor: Striking Mimic of "Classical" Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma.

We report the case of a "fat-rich" (spindle cell-poor) variant of an atypical spindle cell/pleomorphic lipomatous tumor in a 63-year-old female patient presenting with a firm, painless soft tissue mass on the right hip. Atypical spindle cell/pleomorphic lipomatous tumor is a very recently described low-grade adipocytic neoplasm, which occurs predominantly in adults with a predilection for the limbs and limb girdles. In the present case, the diagnosis of an atypical spindle cell/pleomorphic lipomatous tumor was challenging because the tumor was almost exclusively composed of an atypical adipocytic component (resembling "classical" atypical lipomatous tumor/well-differentiated tumor) with only very focal presence of the diagnostic atypical morphologic features (atypical spindle-shaped cells, floret-like multinucleated cells, and "bizarre" pleomorphic [multinucleated] cells). The possibility of a "classical" atypical lipomatous tumor/well-differentiated liposarcoma was ruled out by immunohistochemistry (lack of MDM2 expression and loss of Rb expression) and molecular genetic testing (no amplification of MDM2 and presence of monoallelic deletion of RB1). Another interesting morphologic observation in this case was the striking perivascular location of the atypical spindle/pleomorphic cells in some areas (so-called "pericytic mimicry"). To our knowledge, pericytic mimicry has not been reported in the setting of an atypical spindle cell/pleomorphic lipomatous tumor.

Surgical Treatment of Chronic Parotitis.

Introduction chronic parotitis (CP) is a hindering, recurring inflammatory ailment that eventually leads to the destruction of the parotid gland. When conservative measures and sialendoscopy fail, parotidectomy can be indicated. Objective to evaluate the efficacy and safety of parotidectomy as a treatment for CP unresponsive to conservative therapy, and to compare superficial and near-total parotidectomy (SP and NTP). Methods retrospective consecutive case series of patients who underwent parotidectomy for CP between January 1999 and May 2012. The primary outcome variables were recurrence, patient contentment, transient and permanent facial nerve palsy and Frey syndrome. The categorical variables were analyzed using the two-sided Fisher exact test. Alongside, an elaborate review of the current literature was conducted. Results a total of 46 parotidectomies were performed on 37 patients with CP. Near-total parotidectomy was performed in 41 and SP in 5 cases. Eighty-four percent of patients was available for the telephone questionnaire (31 patients, 40 parotidectomies) with a mean follow-up period of 6,2 years. Treatment was successful in 40/46 parotidectomies (87%) and 95% of the patients were content with the result. The incidence of permanent and transient facial nerve palsy was 0 (0%) and 12 (26.1%), respectively. Frey syndrome manifested in 20 (43.5%) patients. Neither this study nor careful review of the current literature resulted in evident difference between SP and NTP regarding the primary outcome variables. Conclusion parotidectomy is a safe and effective treatment for CP in case conservative therapy fails. There is no evidence of a distinct difference between SP and NTP regarding efficiency, facial nerve palsy or Frey syndrome.

Clear Cell Odontogenic Carcinoma: Occurrence of EWSR1-CREB1 as Alternative Fusion Gene to EWSR1-ATF1.

Clear cell odontogenic carcinoma (CCOC) is a rare, low-grade malignant epithelial neoplasm, occurring in the jawbones, mainly affecting the mandible of elderly patients. In addition to hyalinizing clear cell carcinoma of the salivary gland, it is one of the epithelial neoplasms known to harbor an EWSR1-ATF1 fusion. Therefore, a link between these tumors seems plausible. We describe six cases of CCOC showing EWSR1 rearrangements, with two cases being positive for the ATF1 partner gene using FISH analysis. In one case, an EWSR1-CREB1 fusion was identified using RT-PCR, which we report for the first time in this tumor type. The other three cases investigated by FISH were negative for ATF1, CREB1 and CREB3L2. In conclusion, our data show that EWSR1-CREB1 is an alternative fusion gene to EWSR1-ATF1 in CCOC.