Infrequent Tumor Research Articles

Giant benign mesenteric cysts (mesothelioma and lymphangioma): A report of two cases

Introduction and importanceMesenteric cysts are a rare group of intra-abdominal tumors located in the mesentery or omentum, most of this lesion are asymptomatically but occasionally presents with non-specific symptoms, which makes diagnosis difficult. Case presentationWe present two cases of giant mesenteric cyst in our Institution, the first case is a women of 23 years with previous gynecologic surgery with chronic abdominal pain and large abdominal mass CT showed a giant intraabdominal 30 × 25 × 15 cm, the patient went to laparotomy and a large mesenteric tumor found. The Histopathology reported a Benign cyst mesothelioma (BCM). The second case is a 47 year male with intermittent abdominal pain and abdominal CT shows a 20x21x15 cm tumor. Laparotomy was performed. Histopathology reported a large lymphangioma. Clinical discussionBCM tumors are rare intrabdominal lesions often diagnosed in premenopausal women. Its etiopathogenesis is still unclear, associated risk factors are endometriosis, pelvic inflammatory disease and previous pelvic surgery. Lymphangiomas are an infrequent cyst tumors. It results from a failure in the evolutionary development of the lymphatic system, often localized in the head and neck and its localization in the abdomen is even rare. The definitive diagnosis is made by histopathology. ConclusionMesenteric cysts diagnosis if often challenge due to nonspecific symptoms and significant overlap in imaging appearance between the different entities, its diagnosis should be in mind when encounter a cystic abdominal tumor, surgical complete removal of this tumors is the optimal treatment to prevent recurrence and complications.

Neoadjuvant Treatment in Locally Advanced Thyroid Carcinoma.

Although the focus in the last decades has been on the overdiagnosis of incidentally detected thyroid carcinomas in early stages, the other extreme of the disease is represented by locally advanced tumors with the invasion of neighboring structures. These are infrequent tumors, but they have a high complexity and a poor prognosis. In the absence of effective therapies allowing preoperative tumor reduction, in order to achieve a more restricted surgery, treatment was limited to aggressive surgery with resection of the aerodigestive tract and major vascular structures or palliative treatment. However, due to the increased knowledge of tumor biology and the results that tyrosine kinase inhibitors have achieved in the treatment of radioactive iodine-refractory tumors, neoadjuvant therapy with a curative intent has emerged as a reality to be taken into account when dealing with these patients. This paper presents a narrative review of the current scientific evidence regarding neoadjuvant treatment in locally advanced thyroid cancer.

Malignant salivary gland tumors of the tongue: A multicenter REFCOR study.

Salivary carcinomas of minor salivary glands are very infrequent tumors. When located in the tongue, the therapeutic strategy may comprise upfront surgery, which may be debilitating, and/or (chemo-)radiotherapy. The aim of this study was to identify the prognostic factors of salivary carcinomas of the tongue in a population-based cohort. This retrospective multicentric study, based on the "Réseau d'Expertise Français sur les Cancers ORL Rares" (REFCOR), included all the patients with a salivary carcinoma of the tongue, diagnosed between January 2009 and December 2018. Dubious slides were reviewed by REFCOR expert pathologists to ensure diagnostic accuracy. Treatment was performed in accordance with national REFCOR recommendations. From 28 centers, 103 patients were included in this study. Median age at diagnosis was 63 years, and 60.2% were female. Tumors were adenoid cystic carcinomas (41.7%), mucoepidermoid carcinomas (30.1%), and other adenocarcinomas (28.2%). Primary treatment was surgical for 61.2% of them. Five-year overall survival (OS) and event-free survival (EFS) rates were 84.7% and 38.6%, respectively. In multivariable analysis, EFS was significantly worse in case of nonsurgical treatment, alcohol consumption, and glossotonsillar sulcus involvement. N-positive status was the only significant prognostic factor for OS in multivariable analysis. Salivary carcinomas of the tongue represent a heterogeneous group of rare tumors, with a high risk of recurrence. In this national cohort, surgery was associated with better EFS and N-status was the main independent prognostic factor for OS.

Stereotactic Radiosurgery for Residual, Recurrent, and Metastatic Hemangiopericytomas: A Single-Institution Retrospective Experience.

Hemangiopericytomas are infrequent vascular tumors originating from Zimmermann pericytes. The conventional treatment involves gross total resection, followed by adjuvant radiotherapy. Nevertheless, their tendency to infiltrate dural sinuses, high vascularity, and anatomic complexity pose challenges for radical resection, leading to a significant risk of recurrence. Stereotactic radiosurgery (SRS) has emerged as a promising adjuvant therapy to address these challenges. Our study provides the largest single-institutional retrospective, aiming to evaluate the effectiveness and safety of SRS as a treatment modality for residual, recurrent, and metastatic hemangiopericytomas. From 1998 to 2023, 27 patients with 101 tumors underwent CyberKnife SRS at Stanford University Medical Center. The median age was 51 years at the time of treatment. The median follow-up period from SRS was 103 months (range: 6-250). All patients underwent upfront surgical resection. The median tumor volume was 1.5 cc. The median single-fraction equivalent dose was 19 Gy. The SRS was administered at the 76% of the median isodose line (range: 64-89). Of the 101 treated tumors, 24 (23.8%) progressed with a median time to recurrence of 30 months. At 10 years, the rates of local tumor control (LTC), overall survival (OS), and progression-free survival (PFS) were 74.3%, 80.8%, and 67%, respectively. In patients with metastatic lesions, the LTC rates were significantly greater when compared with those with residual or recurrent tumors. There was no significant difference between patients with residual, recurrent, and metastatic hemangiopericytomas in OS and PFS. Notably, no cases of radiation-induced adverse events were detected. SRS leads to excellent LTC, PFS, and OS at 10 years with negligible risk for adverse events. Therefore, it is an effective and safe management modality for patients with residual, recurrent, and metastatic hemangiopericytomas.

Proteomic analysis of pleomorphic dermal sarcoma reveals a fibroblastic cell of origin and distinct immune evasion mechanisms

Pleomorphic dermal sarcomas are infrequent neoplastic skin tumors, manifesting in regions of the skin exposed to ultraviolet radiation. Diagnosing the entity can be challenging and therapeutic options are limited. We analyzed 20 samples of normal healthy skin tissue (SNT), 27 malignant melanomas (MM), 20 cutaneous squamous cell carcinomas (cSCC), and 24 pleomorphic dermal sarcomas (PDS) using mass spectrometry. We explored a potential cell of origin in PDS and validated our findings using publicly available single-cell sequencing data. By correlating tumor purity (TP), inferred by both RNA- and DNA-sequencing, to protein abundance, we found that fibroblasts shared most of the proteins correlating to TP. This observation could also be made using publicly available SNT single cell sequencing data. Moreover, we studied relevant pathways of receptor/ligand (R/L) interactions. Analysis of R/L interactions revealed distinct pathways in cSCC, MM and PDS, with a prominent role of PDGFRB-PDGFD R/L interactions and upregulation of PI3K/AKT signaling pathway. By studying differentially expressed proteins between cSCC and PDS, markers such as MAP1B could differentiate between these two entities. To this end, we studied proteins associated with immunosuppression in PDS, uncovering that immunologically cold PDS cases shared a “negative regulation of interferon-gamma signaling” according to overrepresentation analysis.

Occipital intradiploic epidermoid cyst

Intradiploic epidermoid cysts are rare intracranial tumours, with an estimated prevalence of less than 1% of all cranial tumours. Most of the intradiploic cysts are asymptomatic; however, clinical findings consist of headache and tenderness. We presented a case of a 21-year-old female who consulted the neurosurgery department for a period of three years about a mass in the occipital region, which was growing gradually. The patient was treated with surgical removal without complications. Intradiploic epidermoid cysts are infrequent intracranial tumours that primarily affect adults. This tumour has a wide spectrum of symptoms. Radiologic findings on computed tomography (CT) and magnetic resonance imaging (MR) are the cornerstone for the diagnosis, which is finally confirmed by histopathological studies. Surgical management with a complete resection of the cyst and capsule is the most commonly used treatment.

Thoracic lipoblastoma in a 6-year-old African male: a case report.

Lipoblastoma is a very infrequent tumor, characteristic of early childhood. The thoracic location is infrequent, with isolated reports to date. We present the case of a 6-year-old male patient with a right thoracic tumor of months of evolution that was surgically removed by right anterolateral thoracotomy and in which the diagnosis of classic well-differentiated lipoblastoma was histologically confirmed. The patient evolved favorably and was discharged. He is currently under follow-up and without recurrence 1 year after surgery. This is, to our knowledge, the first thoracic lipoblastoma reported in an African pediatric patient. The importance of knowing the clinical, semiological, and intraoperative characteristics of this tumor becomes even more important, as in our case, in the context of international cooperation, where in many cases, there is no possibility of performing pre-operative imaging studies or subsequent genetic studies.

A gene signature linked to fibroblast differentiation for prognostic prediction of mesothelioma

BackgroundMalignant mesothelioma is a type of infrequent tumor that is substantially related to asbestos exposure and has a terrible prognosis. We tried to produce a fibroblast differentiation-related gene set for creating a novel classification and prognostic prediction model of MESO.MethodThree databases, including NCBI-GEO, TCGA, and MET-500, separately provide single-cell RNA sequencing data, bulk RNA sequencing profiles of MESO, and RNA sequencing information on bone metastatic tumors. Dimensionality reduction and clustering analysis were leveraged to acquire fibroblast subtypes in the MESO microenvironment. The fibroblast differentiation-related genes (FDGs), which were associated with survival and subsequently utilized to generate the MESO categorization and prognostic prediction model, were selected in combination with pseudotime analysis and survival information from the TCGA database. Then, regulatory network was constructed for each MESO subtype, and candidate inhibitors were predicted. Clinical specimens were collected for further validation.ResultA total of six fibroblast subtypes, three differentiation states, and 39 FDGs were identified. Based on the expression level of FDGs, three MESO subtypes were distinguished in the fibroblast differentiation-based classification (FDBC). In the multivariate prognostic prediction model, the risk score that was dependent on the expression level of several important FDGs, was verified to be an independently effective prognostic factor and worked well in internal cohorts. Finally, we predicted 24 potential drugs for the treatment of MESO. Moreover, immunohistochemical staining and statistical analysis provided further validation.ConclusionFibroblast differentiation-related genes (FDGs), especially those in low-differentiation states, might participate in the proliferation and invasion of MESO. Hopefully, the raised clinical subtyping of MESO would provide references for clinical practitioners.

Role of Radiation Therapy in Management of Isolated Myeloid Sarcoma: Report of a Case and Review of the Literature

Myeloid sarcoma is an infrequent extramedullary tumor originating from immature myeloid cells and is associated with acute non-lymphocytic leukemia or myelodysplastic syndrome. Recent years have seen advancements in the survival rates of leukemia patients, primarily attributed to a deeper comprehension of the genetic underpinnings of the disease and the development of more effective combinations of chemotherapy and targeted therapies. Notably, the ability to achieve lasting control over systemic disease within the blood and bone marrow has markedly contributed to improved survival rates. However, the emergence of extramedullary relapses can present challenging therapeutic situations, where radiation therapy emerges as a crucial intervention. In light of these considerations, we report the case of a 67-year-old patient, with a history of acute leukemia treated in 2019 in remission and who presents an extramedullary blast localization at the level of the left elbow treated locally by radiotherapy and we have conducted a comprehensive literature review aimed at evaluating the potential role of radiotherapy in managing this rare manifestation of leukemia.

Intracranial solitary fibrous tumor in a 15-year-old girl: illustrative case.

Solitary fibrous tumor (SFT) is an infrequent spindle cell tumor derived from mesenchymal tissue, which can manifest in diverse anatomical locations, primarily in the pleural cavity and infrequently in the central nervous system. SFT is predominantly observed in individuals aged between 40 and 50 years old, with a slightly higher occurrence in males than in females. This case report describes a female, age 15, who had migraines for 2 months prior to the diagnosis of an intracranial tumor. Computed tomography and magnetic resonance imaging showed a mass located in the right parietooccipital region with surrounding edema and a compressed right lateral ventricle. Neurosurgery was utilized to successfully remove the mass, and single intracranial fibrous tumor (grade I) was identified by postoperative pathological analysis. During an 8-month follow-up period, the patient did not experience any recurrences. SFT is often misdiagnosed as meningioma because of their similar imaging characteristics. However, identifying the distinctive features of SFT on magnetic resonance imaging can distinguish it from meningioma and help to select appropriate treatment. The complete preoperative imaging data for this case indicated a highly vascularized tumor. Preoperative vascular embolization treatment reduced any difficulties during the subsequent tumor resection and minimized intraoperative bleeding.

Peripheral Orbital Schwannoma : A Case Report

Introduction : The aim of this study was to report a rare case of a peripheral orbital nerve schwannoma. One of a thinkable diagnose and the goal of treatment.
 Case Illustration : A 17-years-old young lady with chief complaint was inferior eyelid lesion since 1 year and has gradually enlarged. Examination showed a space occupying lesion in the inferior right orbit around 10x5 mm that was firm to palpation, didn’t attach to the deep planes, painless, and did not displaced the eye. Computed tomography revealed a homogenous orbital mass, encapsulated, and did not invade adjacent structures
 Discussion : Lesion was treated with complete tumour resection via conjunctival / posterior site, and pathologic examination showed a schwannoma.Conclusion : Orbital schwannoma are infrequent tumours arising from the orbit coming behind inflammatory, vascular, and lymphoproliferative diseases. Treatment is complete resection of the lesion with subsequent monitoring to prevent recurrence.

Bednar’s tumor at right shoulder in an adult male: a case report of a rare entity

Introduction and importance: Bednar tumor, a rare variant of dermatofibrosarcoma protuberans is a tumor with low malignant potential. Owing to limited studies, the pathogenesis and risk factor of this tumor are not clearly understood. The tumor extends from the epidermis to the dermal layers and even affects the surrounding bone. Here, the authors present a case of a 48-year-old male with a Bednar tumor, which was successfully managed by wide local excision and flap repair. Case presentation: Our patient presented to the hospital after the reappearance of mass, 6 years after the excision of the previously misdiagnosed lipoma. Vitals and systematic examination were normal. Local examination revealed an oval-shaped mass with a glistening surface on the right shoulder. The patient underwent wide excision and skin flap surgery for the treatment, and the diagnosis was confirmed through histopathological examination and immunohistochemistry for the CD34 marker. Clinical discussion: Bednar tumor is an infrequent skin tumor linked to genetic anomalies and is one of the rare variants [(<0.1%) of skin tumors]. Diagnosis can be done by histopathological examination and CD34 marker positivity via immunohistochemistry. This tumor is mistaken for lipoma, leading to recurrent growth postexcision. The tumor demands a broader resection due to the high chances of reoccurrence. Although Mohs micrographic surgery is the ideal approach, its limited availability in resource-constrained settings prompts alternative strategies. Conclusion: This case highlights the challenges of diagnosis, the rarity of the condition, and the need for vigilant follow-up due to the tumor’s propensity for recurrence.

Pediatric Adrenocortical Carcinoma: The Nuts and Bolts of Diagnosis and Treatment and Avenues for Future Discovery.

Adrenocortical tumors (ACTs) are infrequent neoplasms in children and adolescents and are typically associated with clinical symptoms reflective of androgen overproduction. Pediatric ACTs typically occur in the context of a germline TP53 mutation, can be cured when diagnosed at an early stage, but are difficult to treat when advanced or associated with concurrent TP53 and ATRX alterations. Recent work has demonstrated DNA methylation patterns suggestive of prognostic significance. While current treatment standards rely heavily upon surgical resection, chemotherapy, and hormonal modulation, small cohort studies suggest promise for multi-tyrosine kinases targeting anti-angiogenic pathways or immunomodulatory therapies. Future work will focus on novel risk stratification algorithms and combination therapies intended to mitigate toxicity for patients with perceived low-risk disease while intensifying therapy or accelerating discoveries aimed at improving survival for patients with difficult-to-treat disease.

Endometrial carcinoma with co-existing granulosa cell tumour in a post-menopausal woman: a case report

Background: Granulosa cell tumors (GCT) of the ovary are extremely infrequent tumors accounting for about 3% of the entire ovarian malignancies with a very high rate of recurrence. Due to its ability to secrete estrogen unopposed, it can give rise to endometrial cancer thus leading to the coexistence of the two tumors on rare occasions. Case presentation: We present here, the case of a 58-year-old post-menopausal Nigerian woman with GCT coexisting with endometrial carcinoma. She presented with abdominal pain, weakness, and post-menopausal vaginal bleeding. Examination revealed an irregular 30-week size abdominopelvic mass while an abdominopelvic ultrasonography showed a right ovarian mass and multiple uterine fibroids. However, the diagnosis of GCT coexisting with endometrial carcinoma was histologically confirmed. She has been clinically stable for ten months post-surgical intervention and completion of adjuvant chemotherapy (Cisplatin [75mg/m2] and Docetaxel [75mg/m2]). Conclusion: Although rare, GCT can exist synchronously with endometrial carcinoma. This should form an important differential diagnosis in a post-menopausal woman with bleeding par vaginum as this is its most important clinical presentation. Total abdominal hysterectomy with bilateral adnexectomy should be done in older patients with GCT. Additionally, adjuvant chemotherapy may be of tremendous benefit to diagnosed patients.

Molecular Pathogenesis and Histological Variability of Dermatofibrosarcoma Protuberans

Dermatofibrosarcoma protuberans (DFSP) is a kind of infrequent tumor of the soft tissues distinguished by its gradual proliferation and a preference for regional reoccurrence, despite its limited capacity for metastasis. At the molecular level, a significant majority of DFSP cases manifest the t (17;22) (q22; q13) chromosomal translocation, resulting in the fusion of the collagen type I alpha chain (COL1A1) gene and platelet-derived growth factor B chain (PDGFB) gene. This fusion results in PDGFB overexpression, consequently activating the PDGF Receptor-beta (PDGFR-β). The activated PDGFR-β serves as a central nexus for numerous intracellular signaling pathways, initiating cascades including Phosphatidylinositol 3-kinase (PI3K)/Akt, Mitogen-Activated Protein Kinase (MAPK)/extracellular signal-regulated kinase (ERK), and STATs pathways. These cascades collectively enhance DFSP cell growth, proliferation, and invasiveness. Histologically, DFSP tumors are predominantly fibroblastic and display distinct immune cell infiltration patterns in their microenvironment. Elevated expression of CD4+ naïve cells, CD4+ Th2 cells, CD8+ central memory T cells, B cells, and macrophages is evident, while levels of CD4+ central memory T cells and eosinophils are diminished. Immunohistochemical analyses further highlight that most DFSP cells exhibit positive cytoplasmic CD34 expression, whereas factor XIIIa and α-smooth muscle actin are notably absent. Clinically, DFSP presents in diverse subtypes, each characterized by its unique histological profile. Prominent subtypes encompass classic DFSP, fibrosarcomatous DFSP (FS-DFSP), pigmented DFSP, giant cell fibroblastoma, myxoid DFSP, atrophic DFSP, and the granular cell variant. This review aspires to deliver an exhaustive insight into DFSP, accentuating its molecular underpinnings and clinical presentation, with the ultimate goal of advancing our understanding and management of this distinct dermatological entity.

Recurrent cementoblastoma in mandibular first molar region: A case report

Benign cementoblastoma is an infrequent tumor originating from odontogenic mesenchyme. It is distinguished by the presence of a mineralizing mass located at the apex of the tooth root. Adults and children are most commonly affected by this neoplasm. This case report presents of such a rare case of cementoblastoma in lower left molar region causing deflection of inferior alveolar nerve in a 10-year-old female patient presenting with extraoral swelling and complaining of pain in same region for which the patient had previously underwent excision of the tumor incompletely.

Brazilian Non-Hodgkin T Cell Registry: An Exploratory Analysis of Extranodal Sites

Introduction: T cell lymphomas (NHL-T) account for 10-15% of all non-Hodgkin lymphomas (NHL). They are a heterogeneous group of infrequent neoplasms with a variable clinical course but prevalently aggressive behavior and high mortality rates. Diagnosis is still challenging and there has been little change in the overall prognosis over the last two decades. In spite of IPI (International Prognostic Index) that include extranodal (EN) site in its variables, lack is known regarding EN involvement in nodal peripheral T cell lymphomas- PTCL (PTCL-NOS, TFH and ALCL ALK+/ALK-) location or impact on prognosis). Objective: We aim to evaluate number of extranodal (EN) sites in nodal PTCL lymphomas (PTCL-NOS, TFH and ALCL ALK+/ALK-) and its specific location as a surrogate for overall survival (OS) and progression free survival (PFS). Also generate hypothesis for further molecular analysis. Methodology: Brazil T-cell project is a national, ambispective study of patients with histological diagnosis of PTCL diagnosed from January 2015 to December 2022. Approval for the study was obtained at the coordinating center (Samaritano Hospital - São Paulo) and at each participating center as per the institutional standard before initiation. Those selected for the study were previously untreated patients age ≥ 19 years, with de novo PTCL or natural killer/T-cell lymphoma. At each institution, the local pathologist reviewed the diagnose. Clinical information included coded patient and site identifiers, sex, date of birth, date and site of diagnostic biopsy, sites of disease, EN (location and number), methodology of staging (clinical, CT or Pet) and Ann Arbor stage. Initial therapy and response; details of remission, progression, or relapse; and subsequent therapies, along with survival status and cause of death. Treatment outcome was determined by OS and PFS. REDcap Platform (by Vanderbilt) has been used to collect and store data and for descriptive analysis the IBM-SPSS version 24 was applied. Kaplan-Meier method estimated the OS, whereas Log-Rank tests to compare its curves. This trial is registered at Clinical trials (NCT03207789). Results: Of 621 registered we selected 198 patients (pts) diagnosed with nodal PTCL with at least one EN involvement [Cohort 1 EN involvement equal to one (148 pts) and Cohort 2 EN involvement ³ 2 (50 patients)]. Considering all 198 pts (Cohort 1 and 2) there was a slight male predominance (63%); median age 53 years; 79% were staged III or IV; 81.5 were IPI 2 or more. Most frequently histology was PTCL-NOS (46%), followed by ALCL ALK+ (32%), ALCL ALK- (12.5%) and TFH (9.5%). The majority had B Symptoms (63%); 37.5% had Bone Marrow infiltration. The chemotherapy most frequently chosen were CHOEP (54.5%) followed by CHOP (19.5%). Transplant was used as consolidation in 20% of the cases. Almost half of patients achieved complete response after first line (44%), although 38% relapsed. Cohort 1 (EN=1) and 2 (EN ³ 2) were similar regarding clinical characteristics, except, for stage III-IV (73% vs 96%; p <.0001); IPI ³ 3 (37.5% vs. 82%; p <.0001) and ECOG (22 vs. 48%; p=.001), respectively. Therefore, translating in a more advanced disease in Cohort 2. The most common extranodal location in Cohort 1 (EN=1) was Skin/ Subcutaneous (35%), followed by gastrointestinal tract (18%) and lung (16%). NHL-T subtypes behaved similarly in this EN exploratory analysis, with a better OS and PFS in ALCL ALK+, followed by ALK- and PTCL-NOS. There was no difference in PFS in Cohort 1 (EN=1) and 2 (EN ³ 2), but there was a slight difference in Overall survival (55% vs. 42% in 12 months; p=0.06), suggesting EN sites involvement assessed by CT and PET-CT as possible surrogate for outcomes in this population. Conclusion: NHL-T is still unmet medical need considering suboptimal outcome in treatment and survival. New biological and clinical finding are still necessary to adequate stratify this group of patients, considering poor performance of IPI and PIT scores. Number and location of EN sites involvement may be a possible surrogate for outcome, which can be a reflect of a distinct biology, that needs further investigation. Registries are of importance considering rarity and poor prognosis of this diseases and an adequate instrument to hypothesis generation.

Salivary gland tumor incidence in adult patients in a tertiary hospital in Mexico from 2008 to 2019.

To determine the incidence of salivary gland tumors in a population of a tertiary hospital in the State of Mexico, and to describe demographic variables. An observational, cross-sectional and retrospective study of salivary gland tumors reported in a tertiary hospital in the State of Mexico in the period 2008-2019 is presented. A prevalence of 0.049% was found. There was no difference between sex in the studied population. Benign salivary gland tumors were the most frequent (86.7%). The age range most affected was 51-60 years. The most frequently found tumor was the pleomorphic adenoma, followed by Warthin's tumor. There was 13.33% of sialolipomas, and one myoepithelioma. There were no cases of sublingual gland tumors or minor salivary glands. Tumors of the major salivary glands are infrequent tumors; population cases from a central Mexican state and their demographic characteristics are presented to contribute to the information found in local and international literature.

Investigation of the methylation changes in the promoter region of RB1 gene in retinoblastoma: Unraveling the epigenetic puzzle in retinoblastoma

Retinoblastoma is an infrequent neoplasm that arises during childhood from retinal nerve cells and is attributed to the biallelic inactivation of the RB1 gene. In conjunction with anatomical anomalies, it is widely acknowledged that epigenetic modifications play a significant role in the pathogenesis of cancer. The association between methylation of the RB1 gene promoter and tumor formation has been established; however, there is currently no scholarly evidence to substantiate the claim that it is responsible for the inheritance of retinoblastoma. The initial hypothesis posited for this work was that familial retinoblastoma disease would be similarly observed in cases with RB1 promotor gene methylation, akin to RB1 mutations. The RB1 gene promoter region was subjected to methylation screening using real-time PCR in individuals diagnosed with familial retinoblastoma but lacking RB1 mutations. The study involved a comparison of the germline methylation status of the RB1 gene in the peripheral blood samples of 50 retinoblastoma patients and 52 healthy individuals. The healthy individuals were carefully selected to match the retinoblastoma patients in terms of age, sex, and ethnicity. The data obtained from both groups were subjected to statistical analysis. The study revealed that the methylation level in a cohort of 50 individuals diagnosed with retinoblastoma and 52 healthy control participants was determined to be 36.1% and 33.9%, respectively. As a result, there was no statistically significant disparity observed in RB1 promoter methylation between the patient and control groups (p = 0.126). The methylation of the promoter region of the RB1 gene in familial retinoblastoma does not exert any influence on the hereditary transmission of the disease.

RADT-35. STEREOTACTIC RADIOSURGERY FOR RESIDUAL, RECURRENT, AND METASTATIC HEMANGIOPERICYTOMAS: A SINGLE INSTITUTION EXPERIENCE

Abstract INTRODUCTION Hemangiopericytomas are infrequent vascular tumors originating from Zimmermann pericytes. The conventional treatment approach involves gross total resection (GTR), followed by adjuvant radiotherapy. Nevertheless, due to their tendency to infiltrate dural sinuses, high degree of vascularity, and anatomic inaccessibility, radical resection may be challenging with substantial risk of recurrence. To address this challenge, stereotactic radiosurgery (SRS) has been proposed as a promising adjuvant therapy. Objectives Our study aims to evaluate the effectiveness and safety of SRS as a potential treatment modality in patients with residual, recurrent, and metastatic hemangiopericytomas. METHODS From 1998 to 2023, 27 patients with 101 tumors underwent CyberKnife SRS at Stanford University Medical Center. The median age was 51 years at the time of treatment. The median follow-up period from SRS was 103 months (range: 6-250). All patients underwent upfront surgical resection. The median tumor volume was 1.5 cc. The median single-fraction equivalent dose (SFED) was 19 Gy. The SRS was administered at the 76% of the median isodose line (range: 64-89). RESULTS Of the 101 treated tumors, 24 (23.8%) progressed with a median time to recurrence of 30 months. At 10 years, the rates of local tumor control (LTC), overall survival (OS), and progression-free survival (PFS) were 74.3%, 80.8%, and 67%, respectively. In patients with residual lesions, the LTC rates were significantly greater when compared to those with residual or metastatic tumors. There was no significant difference between patients with residual, recurrent, and metastatic hemangiopericytomas in OS and PFS. Notably, no cases of radiation-induced adverse events were detected. CONCLUSION Our study provides the largest single-institutional retrospective series with hemangiopericytomas treated with SRS. SRS leads to excellent LTC, PFS, and OS at 10 years with negligible risk for adverse events. Therefore, it is an effective and safe management modality for patients with residual, recurrent, and metastatic hemangiopericytomas.