Peripheral Neuroectodermal Tumor Research Articles

Rare Location of Ewing Sarcome: A Case Study

Introduction: Ewing's sarcoma is also known as a primary peripheral neuroectodermal tumour and is a primary malignancy accounting for 5-15% of all malignancies. It can involve all skeletal bones and more rarely soft tissue. The area of predilection of this tumour is the long bones 50-60%; the flat bones mainly the pelvis 20%, while the bones of the foot and the hand constitute an exceptional localization (1), hence the interest to report our case. Clinical presentation: We report the case of an 18-year-old girl who presented with a painful swelling of the right heel evolving for 14 months in a febrile context. The diagnosis of Ewing's sarcoma of the calcaneus was suspected by radiological assessment and confirmed by a histological study after a biopsy. We discuss the clinico-radiological and histological diagnosis of this tumour and its management. Discussion: Ewing's sarcoma described by James Ewing in 1921(2), since then Cook reports only 29 cases of Ewing's sarcoma of the calcaneus in the literature (3), which shows the paucity of the literature concerning this type of calcaneal lesions, and therefore clinicians are unfamiliar with these tumours and therefore a delay in diagnosis, morbidity and amputations unnecessary. It is a tumour with a rapid potential for metastasis, particularly in the lungs, which determines the prognosis of this lesion. Conclusion: Ewing's sarcoma remains a rare disease (4) of which the calcaneus is an exceptional location. It may be misdiagnosed with other lesions, notably calcaneal osteomyelitis.

Rare Childhood Cancer Burden in a Tertiary Care Hospital of Dhaka, Bangladesh

Background: Accurate childhood cancer burden data are crucial for resource planning and health policy prioritization. In Bangladesh we have no national population based cancer registry. Data about the total burden of childhood cancer in our country is unknown. But a hospital based cancer registry is the cheapest way to assess the tumor burden of a nation. So we investigate the total pediatric cancer burden and the percentage of different types of rare childhood cancers (RCC) of National Institute of Cancer Research and Hospital (NICRH), Dhaka, during the year 2014 – 2018. Aim: To investigate the total number of pediatric cancers, frequency of different types of rare cancer and percentage of rare childhood cancer in the Pediatric Hematology and Oncology (PHO) department. Methods: Data were collected from all pediatric (0-17 years) patients between the year 2014 and 2018 prospectively. Definitive diagnosis of cases were established by histopathological and or immunohistochemical study. As we have no population-based cancer registry, we considered the rare tumors in our study according to the Children's Oncology Group (COG) and the German Childhood Cancer Registry (GCCR). Results: Total number of childhood cancers and RCC was 2242 and 351 respectively. Percentage of rare tumors was 15.66% in our center. Benign rare tumors were 18.52% (N-65) cases. Common age group was the 5-9 years group (54.13 %). Most common RCC groups were Non-Rhabdomyosarcoma soft tissue sarcoma (NRSTS) constituting 49.29 %, followed by Malignant epithelial neoplasms and melanomas (38.18%). Diagnostic delay was 3.52 months. Most common malignancy was Synovial Sarcoma (N-40, 11.39%), Peripheral Neuroectodermal Tumor (N-39, 11.11%), Nasopharyngeal carcinoma (N-35, 9.97%), Malignant small round cell tumor (N-31, 8.83%) and Carcinoma rectum and colon (N-23, 6.55%). Conclusion: We have found that our Institutional (NICRH) rare tumor rate (15.66%) was a bit higher than US national RCC (15%). Though Institutional cancer data reflect the national burden, to estimate the accurate number and percentage of RCC, National Cancer Registry is needed.

A Case Report on Malignant Rhabdoid Round Cell Tumor in Pelvis

The malignant neoplasm is called as malignant rhabdoid tumor or renal tumor. The Malignant tumor had the highest rate of proliferation. Tiny, round, and generally undifferentiated cells make up malignant small round cell tumours. A round cell tumor is a group of malignant tumors composed of relatively small and undifferentiated cells with an increased nuclear - cytoplasmic ratio. Soft tissue malignant tumours of the abdomen and pelvis are a rare but serious kind of cancer. Examples of these tumours include Ewing's sarcoma, peripheral neuroectodermal tumour, rhabdomyosarcoma, synovial sarcoma, non-lymphoma, Hodgkin's retinoblastoma, neuroblastoma, and hepatoblastoma. Mast cell tumour, histiocytoma, lymphoma, plasmacytoma, and transmissible venereal tumours are some of the different types of round cell tumours. Melanomas are the cytologic "great impostor," as they might look on cytology as round cell tumours despite being classed as mesenchymal cancers. Rhabdoid tumours have long been thought to be extremely malignant and have a bad prognosis. Children with this form of tumour have a six to eleven-month median survival duration. They're also less common. In 5% of small round cell tumor patients, can be curable, and it is best achieved by combining systemic chemotherapy with thorough cytoreductive surgery. Here we report a 9-year-old female child who was diagnosed with a malignant rhabdoid round cell tumor in the pelvis. She has undergone excision of pelvic floor tumor andfurther managed with Chemotherapy.

Prevalence of Small Round Cell Tumors in Pediatric Age Group in the last 10 Years Registered in Al- Najaf Governorate

Malignant small round cell tumors (MSRCT) are referred to as tumors made up of malignant small round cells. The cells in this type of neoplasms are tiny, rounded, and largely undifferentiated. Ewing's sarcoma (ES), peripheral neuroectodermal tumor, rhabdomyosarcoma, non-Hodgkin lymphoma, retinoblastoma, neuroblastoma, hepatoblastoma, and nephroblastoma are a few of the more common ones. The aim of this study is to estimate the prevalence and types of pediatric small round cell tumors in Najaf Province/Iraq, over the 10 years period between 2010-2019. Method: This is a retrospective observational study. Cases were collected from pathology laboratories in As-Sadr Medical City and some private laboratories in Najaf over a 10 year-period extending from 2010 to 2019. Results: A 6366 pediatric surgical biopsy cases were reported during the study period and this represent 8.7% of all cases. Out of these cases, 108 cases with small round cell tumors (SRCT) have given a prevalence rate of 17 per 1000 pediatric cases and 1.5 per 1000 of total (73504) adult and pediatric cases during the same period. The mean age of these SRCT cases was 6.3± 1.6 (range: one month-19) years. The higher proportion of cases was reported in the age of 1-5 years, contributed for 43.5%. Male to female ratio is 59/108 vs. 49/108, respectively, the male to female ratio being at 1.2 to 1.0. Conclusions: The mean age of SRCTs cases was 6.3± 1.6, ranging from one month to 19 years. The higher proportion of SRCTs cases was reported in the age ranging from 1-5 years; with a ratio of males to females being 1.2 to 1.0.

Peripheral Primary Neuroectodermal Tumour of the Ileum: A Case Report and Review of the Literature

Background: Ewing’s Sarcoma (ES)/peripheral Primitive Neuroectodermal Tumor (pPNET) is a rare aggressive malignant small round cell tumour. Most of them arise in bony sites, and they represent the second commonest primary osseous malignancy in adolescence and young adults. The localization of the small bowel is very rare, to our knowledge only 35 cases of ES/pPNET of the small bowel have been reported in the literature. Case Presentation: We report a case of pPNET of the ileum in a 26-year-old female, presented abdominal pain with a transit disorder. The clinical examination was unremarkable. The histological and immunohistochemical study confirmed the diagnosis of peripheral primary neuroectodermal tumours. The patient was treated by tumor resection followed by adjuvant chemotherapy. The evolution was good, without recurrence with a follow-up of 12 months. Conclusion: PNET of the ileum is very rare. We report this case to enrich the database of this rare clinical entity and to improve the management of patients with PNET of the ileum.

Extraosseous Ewing's Sarcoma of the Maxillary Sinus: A Very Rare Entity

AbstractEwing's sarcoma is rare sarcoma of bone and soft tissue that uncommonly involve the head and neck in both bone and soft tissue locations. The term Ewing's sarcoma family of tumors comprises both Ewing's sarcoma and peripheral neuroectodermal tumor. It was in 1975, Angervall and Enzinger described the Ewing's sarcoma arising in soft tissues (extraskeletal). The principal sites of extraskeletal Ewing's sarcoma are the paravertebral region and chest wall, generally in close association with vertebrae or the ribs. These tumors may also arise in the soft tissues of the lower extremities and rarely in the pelvic region and hip regions. Superficially located cases do occur but are rare. Here, we present a case of Ewing's sarcoma involving the maxillary sinus region. A 12-year-old boy reported to our department with a swelling on the right side of middle third of the face for 15 days. Intraorally, there was only obliteration of the labial vestibule. On histopathological examination, a provisional diagnosis of malignant round cell tumor was given. Immunohistochemistry with a panel of markers was done to come to a definitive diagnosis. CD99 positivity confirmed the diagnosis of Ewing's sarcoma.

Adult peripheral primary neuroectodermal tumor: a case report and literature review

Objective: To analyze the clinical features, diagnosis and differential diagnosis of peripheral primary neuroectodermal tumor(pPNET). Methods: The clinical data and diagnosis of a patient with rapid progressive pPNET in Shandong Provincial Hospital affiliated to Shandong University in January 2016 was reported and the related literatures were reviewed.The literature reviews were carried out respectively in CNKI, Wanfang and PubMed by July 2016 with "primitive neurotodermal tumour" and "PNET" being the search term from March 1994 to July 2016, including 13 articles. Results: A 41 year-old male patient was admitted to the hospital because of shortness of breath and occasional chest tightness, accompanied by general asthenia of about 15 d. Positron emission and transmission-CT of total trunk showed a mass in the right femoral osteoperiosteal mass, and multiple nodules in the left lung, lumps and nodules in the right lung, and right pleural thickening and effusion. Thoracoscopy was performed and pathology study confirmed the diagnosis of peripheral primary neuroectodermal tumor. The patient was given 2 courses of chemotherapy, but had rapid progressive worsening and died 1 month after PNET diagnosis. A total of 13 literatures of PNET were retrieved, all of which were case reports, and a total of 15 cases were reported.There were 9 male and 7 female patients, with a median age of 26 years.The symptoms had no specificity and most of them were solid masses in chest images, with or without pleural effusion. Eight cases were diagnosed by imaging guided percutaneous biopsy, 7 by operation and pathology, and 1 by medical thoracoscopy. Four cases underwent chemotherapy, and the survival time was less than 6 months. Twelve cases got surgical resection: 2 with surgical treatment, 7 with postoperative chemotherapy, 2 with postoperative radiotherapy and chemotherapy, 1 with postoperative chemotherapy and autologous bone marrow transplantation treatment, among which 11 patients completed follow-up. During follow-up, 3 cases died, and the survival time was 10 months, 3 years and 7 years, respectively. Conclusions: PNET is rare.Due to the lack of specificity of clinical manifestations, clinical diagnosis depends on biopsy. Early diagnosis and surgical resection are especially important for prognosis and quality of life.

Valor de la determinación inmunohistoquímica de SMARCA4/BRG1 en el diagnóstico del carcinoma de ovario de célula pequeña variante hipercalcémica. Presentación de dos casos

Small cell carcinoma of ovary-hypercalcemic type is an undifferentiated carcinoma. We describe two cases in women aged 32 and 29. Both presented with large masses and complete surgical extirpation was impossible. Histologically, the images were similar, with diffuse cell proliferation, accompanied by the presence of follicle-like spaces. In both cases it was necessary to make a differential diagnosis with entities such as adult or juvenile granulosa cell tumour, small cell carcinoma of pulmonary type, dysgerminoma and even peripheral neuroectodermal tumour. The absence of SMARCA4/BRG1 immunostaining proved very useful in the diagnosis of hypercalcemic small cell ovarian carcinoma.

Round Cell Tumors: Classification and Immunohistochemistry.

Round cell tumors as the name suggest are comprised round cells with increased nuclear-cytoplasmic ratio. This group of tumor includes entities such as peripheral neuroectodermal tumor, rhabdomyosarcoma, synovial sarcoma, non-Hodgkin's lymphoma, neuroblastoma, hepatoblastoma, Wilms' tumor, and desmoplastic small round cell tumor. These round cells tumors are characterized by typical histological pattern, immunohistochemical, and electron microscopic features that can help in differential diagnosis. The present article describes the classification and explains the histopathology and immunohistochemistry of some important round cell tumors.

Small round cell tumorが疑われた乳児耳下部石灰化上皮腫例

Small round cell tumors are histopathologically characterized by proliferation of small, round, relatively undifferentiated cells. Small round cell tumors are generally malignant tumors, such as Ewing’s sarcoma, peripheral neuroectodermal tumor, rhabdomyosarcoma, synovial sarcoma, non-Hodgkin’s lymphoma, and Wilms’ tumor. Histopathological examination is usually to make a definitive diagnosis of this type of tumor.

Diagnostic utility of cyclin D1 in the diagnosis of small round blue cell tumors in children and adolescents

Small round blue cell tumors (SRBCTs) of children and adolescents are often diagnostically challenging lesions. With the increasing diagnostic approach based on small biopsies, there is the need of specific immunomarkers that can help in the differential diagnosis among the different tumor histotypes to assure the patient a correct diagnosis for proper treatment. Based on our recent studies showing cyclin D1 overexpression in both Ewing sarcoma/primitive peripheral neuroectodermal tumor (EWS/pPNET) and peripheral neuroblastic tumors (neuroblastoma and ganglioneuroblastoma), we immunohistochemically assessed cyclin D1 immunoreactivity in 128 cases of SRBCTs in children and adolescents to establish its potential utility in the differential diagnosis. All cases of EWS/pPNET and the undifferentiated/poorly differentiated neuroblastomatous component of all peripheral neuroblastic tumors exhibited strong and diffuse nuclear staining (>50% of neoplastic cells) for cyclin D1. In contrast, this marker was absent from rhabdomyosarcoma (regardless of subtype) and lymphoblastic lymphoma (either B- or T-cell precursors), whereas it was only focally detected (<5% of neoplastic cells) in some cases of Wilms tumor (blastemal component) and desmoplastic small round cell tumor. Our findings suggest that cyclin D1 can be exploitable as a diagnostic adjunct to conventional markers in confirming the diagnosis of EWS/pPNET or neuroblastoma/ganglioneuroblastoma. Its use in routine practice may also be helpful for those cases of SRBCT with undifferentiated morphology that are difficult to diagnose after application of the conventional markers.

Diagnostic utility of Wilms' tumour-1 protein (WT-1) immunostaining in paediatric renal tumours.

Background & objectives:Renal tumours constitute about 7 per cent of all neoplasms in children. It is important to differentiate Wilms’ tumour (commonest tumour) from non-Wilms’ tumours. The aim of this study was to evaluate the immunoexpression and diagnostic role of Wilms’ tumour-1 protein (WT1) in paediatric renal tumours.Methods:A total of 53 cases of renal tumours in children (below 18 yr) who underwent total nephrectomy were included in this retrospective study. WT1 immunostaining was done using mouse monoclonal WT1 antibody (clone: 6F-H2).Results:Of the 53 cases, 38 (72%) were of Wilms’ tumour. Non-Wilms’ group (15) included six cases of mesoblastic nephroma (MN), two each of clear cell sarcoma (CCSK), renal cell carcinoma (RCC) and peripheral neuroectodermal tumour (PNET) and one each of angiomyolipoma (AML), rhabdomyosarcoma (RMS) and malignant rhabdoid tumour (MRT). Proportion of WT1 positivity in Wilms’ tumour was 100 per cent in contrast to 26.7 per cent in non-Wilms’ tumours (P<0.001). Epithelial and blastemal components of Wilms’ tumour showed moderate (2+) nuclear and cytoplasmic staining in 80 (24/30) and 75 per cent (24/32) cases, respectively. MN, PNET, CCSK and AML were negative for WT1. RMS, RCC and MRT showed cytoplasmic staining, strongest in RMS. No significant association was seen between WT1 expression and NWTSG (National Wilms’ Tumor Study Group) stage.Interpretation & conclusions:WT1 helps to differentiate Wilms’ tumour from other paediatric renal tumours. It may help in differentiating the two subgroups of Wilms’ tumour which have distinct molecular pathogenesis and biological behaviour, however, further prospective studies are required for validation of this hypothesis.

Primitive neuroectodermal tumors of kidney: Our experience in a tertiary care center.

Primitive neuroectodermal tumors (PNET) are rare highly aggressive neoplasms. The diagnosis is made by histopathology with the support of immunohistochemistry (IHC) and cytogenetics. The aggressive multimodality treatment is recommended for the management of these tumors. The purpose of our study is to review our experiences in the diagnoses and treatment of PNET of the kidneys. We retrospectively reviewed the data of all the patients, who were treated for the PNET of the kidneys at our institute between April and March 2011 and compared with the available literature. A total of eight patients were treated for PNET of the kidney. Out of the eight patients, four were males and four females. Nearly 50% of our patients had inferior vena caval thrombus at the time of presentation. The diagnosis was made on histopathology supported by IHC. Out of the eight patients, one patient had intraoperative death due to massive pulmonary thromboembolism and another died on the 7th post-operative day due to disseminated intravascular coagulation and multiorgan failure. Rest six patients were treated with post-operative chemotherapy or a combination of chemotherapy and radiotherapy. For these six patients, overall median survival was 45 months with a 3 year disease-free survival of 66% and 5 year survival of 44%. PNET of the kidneys are rare peripheral neuroectodermal tumors with an aggressive clinical course. These tumors carry a very poor prognosis. An aggressive treatment approach using a combination of surgery, chemotherapy and radiotherapy is recommended for a reasonable survival in these tumors.

High-dose Thiotepa as Consolidation Therapy With Autologous Hematopoietic Stem Cell Transplantation for High-risk Ewing Family Tumors: Single-institution Experience.

High-dose therapy (HDTx) with autologous stem cell rescue has been widely applied in very-poor-risk pediatric solid tumors. Promising data have become available with the use of high-dose busulfan, whereas high-dose (HD) thiotepa is less commonly used. We report retrospectively our single-institution experience from 1986 to 2012 of single and tandem HDTx with special emphasis on HD-thiotepa as the backbone of HD regimen in Ewing family tumors, including all 24 patients in the Helsinki University Hospital referral area in population-based fashion (Ewing sarcoma 9, Askin tumor 9, peripheral neuroectodermal tumor 6). The 10-year overall survival for the entire cohort was 0.73±0.01. Thirteen out of the 24 underwent HDTx (10 single, 3 tandem). The HDTx regimen consisted of HD-thiotepa (900 mg/m), VP16, and carboplatin. Additional HD-melphalan and total body irradiation were used in the tandem regimens. There was no toxic mortality. The 5-year event-free survival was 0.73±0.16 for high-risk cases transplanted in 1CR. In the relapse group, 1 out of the 3 survived. Radiotherapy to axial sites was given safely in combination with HD-thiotepa in all 3 patients. Thiotepa-based HDTx approach resulted in an encouraging outcome without toxic mortality for high-risk patients. HD-thiotepa merits further studies in larger controlled series.

Peripheral neuroectodermal tumour of the kidney (Ewing's sarcoma): Restaging with (18)F-fluorodeoxyglucose (FDG)-PET/CT.

Primitive peripheral neuroectodermal tumour and Ewing's sarcoma (PNET/EWS) were originally described as two distinct pathologic entities, although both share common stem-cell precursor and unique chromosomal abnormality. Although its incidence has increased recently, its share in all sarcomas is 1%. It is usually seen in men and women in their twenties. We present a case of a 38-year-old woman with a left renal mass detected incidentally. Magnetic resonance imaging revealed a centrally located hypervascular renal mass with diameter of 6 cm with non-homogenous contrast enhancement containing necrotic and calcific areas. The patient was diagnosed as having PNET/EWS by histopathological examination following radical nephrectomy. Para-aortic lymph node metastasis was found on imaging by (18)F-fluorodeoxyglucose (FDG)-positron-emission tomography/computed tomography (PET/CT).

Female New-Born with Undifferentiated Sarcoma Defined by Bcor-Ccnb3 Fusion Transcript

A female new-born presented with a sacrococcygeal mass with spinal cord compression. A preliminary histologic diagnosis determined a small round blue cell tumor and immunohistochemical results discarded neuroblastoma, rhabdomyosarcoma, rhabdoid tumor, Ewing or peripheral neuroectodermal tumor (PNET). The results obtained by SNPa showed a chromosome Xp11.4 deletion of 0.9 Mb, where the BCOR gene is located. RT-PCR did not detect the ETV6-NTRK3 or EWSR1-FLI1 fusion, but did reveal the presence of the BCOR-CCNB3 fusion transcript, recently reported in some undifferentiated sarcomas, establishing the diagnosis of “Ewing-like” sarcoma. Analysis of CCNB3 expression by immunohistochemistry showed nuclear overexpression in 100% of tumor cells. The patient received aggressive chemotherapy which reduced the size of the tumor, but ultimately the patient died of liver failure secondary to infection with adenovirus 5 months after diagnosis. While the literature reports the predominance of these tumors in male children or young adults, we present the first case in a female new-born. This finding supports the need for further studies to look for the presence of the BCOR-CCNB3 fusion transcript in younger patients, to achieve an effective sub-classification within undifferentiated sarcomas.

The Rare Presentation of Extraskeletal Ewing's Sarcoma on the Forehead.

The Rare Presentation of Extraskeletal Ewing's Sarcoma on the Forehead.

PO-0363 Askin Tumour:case Report

Introduction Askin tumour is a primitive neuroectodermal tumour of the thoracopulmonary region. Pulmonary location is not common. We report a case of an Askin tumour in a child who presented with worsening breathlessness. Observation A 9 years-old female child with no pathological history, was admitted with severe dyspnea up to one week. A Weight loss was reported. Physical examination showed silence in pulmonary auscultation of the left lung field. A chest X-ray found a left opacity occupying almost the entire of the left lung, mediastinal compression to the right side and nibbled aspect of the fourth rib. Chest Ultrasound showed pleural effusion with finely heterogeneous liquid. Chest CT showed a pulmonary solid tumour with aspect of massive necrosis of the left upper lobe with hemothorax, rib erosion in contact, without lymphadenopathy or vascular invasion or secondary lesion distance. A scano-guided biopsy was performed and immuno-histological examination found a small round cell tumour with morphological aspects favour the diagnosis of primitive peripheral neuroectodermal tumour corresponding to an Askin tumour. The child underwent an intensive chemotherapy and surgery. Conclusion The management of Askin tumour is not well codified. The prognosis of these tumours remains very unfavourable because of their metastatic risk and potential local recurrence.

English

We report a rare case of peripheral neuro-ectodermal tumor (PNET) in lung diagnosed by USG- guided FNAC in lung of a 19 year old male, who presented with cough, hemoptysis and pleuritic chest pain. CT chest showed a homogeneous mass in left posterior segment of lung with areas of necrosis. CT abdomen and bone scan studies were normal. Fine needle aspiration (FNA) revealed cellular smears comprised of small round blue cells arranged in rosettes, sheets, blue cells having fine chromatin, scant cytoplasm in an inflammatory background. Biopsy was advised for evaluation of small round blue cell to further typing and confirmation for further management. CT-guided trucut biopsy revealed lesion with small round blue cells had round nuclei, fine chromatin with scant cytoplasm arranged in sheets, rosettes in thin fibrous septae. Immunohistochemistry (IHC) showed malignant cells were positive for CD 99, synaptophysin and chromogranin and negativity for CD45 and Cytokeratin.

Intimal Sarcoma Is the Most Frequent Primary Cardiac Sarcoma

We report novel molecular and pathologic features of sarcomas involving the heart. Intimal sarcoma appears as the most frequent primary cardiac sarcoma within the largest described series of 100 primary cardiac sarcomas. Immunohistochemical analysis, fluorescence in situ hybridization, real-time polymerase chain reaction, and array-comparative genomic hybridization were performed on materials from 65 women and 35 men, aged 18 to 82 years (mean 50 y), retrieved from the French Departments of Pathology, between 1977 and early 2013. Right and left heart was involved in 44 and 56 cases, respectively. There were 42 intimal sarcomas, 26 angiosarcomas, 22 undifferentiated sarcomas, 7 synovial sarcomas, 2 leiomyosarcomas, and 1 peripheral neuroectodermal tumor. All but 1 angiosarcomas originated from the right heart, whereas 83% of the intimal sarcomas and 72% of the undifferentiated sarcomas were from the left heart. MDM2 overexpression was immunohistochemically observed in all intimal sarcomas, as well as in 10 of the 22 undifferentiated sarcomas and in 5 of the 26 angiosarcomas. MDM2 amplification was only demonstrated in intimal sarcomas. Genomic analysis showed a complex profile, with recurrent 12q13-14 amplicon involving MDM2, 4q12 amplicon involving KIT and PDGFRA, 7p12 gain involving EGFR, and 9p21 deletion targeting CDKN2A. Immunohistochemical detection of MDM2 overexpression can easily detect intimal sarcoma, provided that molecular aberration is proved. As resections are limited to the left atrium, this histologic subtype could benefit from therapies targeting PDGFRA or MDM2.