Large Anterior Mediastinal Mass Research Articles

The Cystic Appearance of a Mediastinal Mass Does Not Exclude Lymphoma: A Case Example of Classic Hodgkin Lymphoma in a Thymic Cyst and a Brief Literature Review

AbstractHerein, we report a case of a 16-year-old girl who presented with an episode of shortness of breath while playing sports. Upon radiologic workup, she was found to have a large multicystic anterior mediastinal mass. The cystic appearance of mass and lack of constitutional symptoms contributed to favoring a benign cystic process and deferring surgical resection until the end of sport season. When surgery was performed 3 months later, microscopic examination showed findings diagnostic of classic Hodgkin lymphoma arising in a thymic cyst. Despite the rarity of such cases, it is important to remember that the cystic nature of an anterior mediastinal mass does not exclude lymphoma. Definitive diagnosis is not possible without examination of representative tissue.

Primary thymic adenoid cystic carcinoma with high-grade transformation: A clinicopathological and immunohistochemical analysis of 4 cases

Four cases of a distinct carcinoma of the thymic gland are presented. The patients were 4 adult males with an age range from 40 to 47 years (mean, 43.5 years). Clinically, all patients presented with non-specific respiratory symptoms. None of the patients had any prior history of head and neck neoplasm or surgery in that anatomic area. Large anterior mediastinal masses were found on diagnostic imaging with concurrent metastatic disease to pleura, lungs, regional lymph nodes and bones. Microscopically, all tumors were composed of a solid proliferation of hyperchromatic, monomorphic small cells with focal cytoplasmic clearing embedded in a fibromyxoid stroma. In one case, occasional duct-like structures were identified. Immunohistochemically, the tumors were positive for pancytokeratin, CD117 and MYB and negative for myoepithelial markers. Systemic chemotherapy was initiated in all patients. Despite therapy, clinical follow-up revealed that all 4 patients died of their disease 11–23 months after their initial diagnosis. The cases in this series highlight a tumor that is different from conventional thymic carcinoma and that has the morphological and immunohistochemical features commonly seen in adenoid cystic carcinomas with high-grade transformation. Correct diagnosis is essential for patient management.

Progress in treatment of primary mediastinal large B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is an aggressive B-cell lymphoma originating from the thymus, which has different clinical and biological characteristics from diffuse large B-cell lymphoma, NOS. PMBCL tends to occur in young women, usually presenting as a large anterior mediastinal mass. Most patients are in stage Ⅰ-Ⅱ at the time of presentation. There is no standard prognostic scoring system for PMBCL. Immunochemotherapy is commonly used in the treatment of PMBCL, but the optimal first-line treatment has not been determined, and the status of radiotherapy is controversial. The value of PET-CT guided therapy needs to be further verified. Relapsed/refractory PMBCL has a poor prognosis, while novel therapies such as PD-1 inhibitors, brentuximab vedotin, and CAR-T can help improve survival in these patients.

Giant cervicomediastinal non-functioning parathyroid cyst: A rare case

Parathyroid cysts of cervicomediastinal location are rare with only a few cases reported in the international literature. We present a rare case of parathyroid cyst in a 57 years old female with gradually increasing neck swelling and dysphagia. Examination revealed about 5 cm anterior neck swelling which moves with swallowing. Blood results including tumor markers and calcium levels were all unremarkable. Chest radiography noted visible mass with cervicothoracic sign and right tracheal deviation. A computed tomography showed a large anterior mediastinal cystic mass with left supraclavicular extension, size 5 x10 x 14cm pushing trachea to the right side from thyroid cartilage till carina level. She successfully underwent left subtotal thyroidectomy (for coexisting thyroid nodules) and median sternotomy and cyst excision. Operative histopathological examination revealed a parathyroid cyst. The patient’s symptoms were relieved after surgery. Parathyroid cyst can therefore present as a rare cause of neck and mediastinal cystic lesion.

SEVERE PRURITUS AS A PRESENTING SYMPTOM OF HODGKIN'S LYMPHOMA

<h3>Introduction</h3> Pruritus has a broad differential diagnosis. Rarely, this symptom may be the sole manifestation of an underlying malignancy. A patient with 5 years of severe upper body pruritus with no other systemic symptoms was subsequently diagnosed with Hodgkin's lymphoma. <h3>Case Description</h3> A 43-year-old male presented to the allergy-immunology clinic for evaluation of severe pruritus of 3 years' duration; he reported nocturnal worsening awakening him from sleep. The pruritus was refractory to antihistamines but was partially responsive to ice packs. There were no associated constitutional or respiratory symptoms, or lymphadenopathy. CBC with differential and CMP were normal. Omalizumab therapy was administered for 3 months; however, the severe pruritus persisted. Neuropathy work-up by neurology was negative. Dermatology evaluation yielded a diagnosis of folliculitis. Work-up for auto-immune disease by rheumatology was negative. After a total of 5 years of pruritus without identifiable cause, he presented for evaluation of a new-onset supraclavicular mass. Chest CT revealed a large anterior mediastinal mass and a massive conglomerate of lymph nodes. Subsequent biopsy revealed classic Hodgkin's lymphoma. <h3>Discussion</h3> This case underscores that persistent pruritus may be the presenting symptom of malignancy. Pruritus associated with malignancy is classically refractory to antihistamines and may not be accompanied by classic systemic symptoms. While rare, it is important to keep this atypical presentation of malignancy in the differential.

Spindle cell thymoma (WHO type A) - Choriocarcinoma: An unusual association: A clinicopathological and immunohistochemical study of 3 cases.

Three cases of an unusual association between spindle cell thymoma (WHO type A) and choriocarcinoma are presented. The patients are three men between the ages of 58 and 68 years. Clinically, all the patients presented with non-specific symptoms of cough, dyspnea, and chest pain. Clinical history and physical examination did not reveal the presence of any prior malignancy. Diagnostic imaging showed in the three patients the presence of a large anterior mediastinal mass. A core needle biopsy was obtained in the three patients. In two patients the biopsy showed the classic histology of a spindle cell thymoma while in one patient the biopsy showed the association of two tumors - spindle cell thymoma and choriocarcinoma. Surgical resection via thoracotomy was performed in the three patients. The mediastinal tumors measured between 9 and 17cm in greatest diameter and were described as solid and lobulated with areas of hemorrhage. Histologically, all the tumors showed similar histological features of spindle cell thymoma (WHO type A) associated with a high-grade neoplasm composed of round and multinucleated giant cells compatible with choriocarcinoma. Immunohistochemical stains showed positive staining for keratin 5/6, and p40 in the spindle cell component, while the choriocarcinomatous component showed positive staining for human chorionic gonadotropin and human placental lactogen. The cases herein presented highlight not only the unusual association of spindle cell thymoma and choriocarcinoma but also raises some issues regarding the histogenesis of germ cell tumors, in this case choriocarcinoma.

147 Synchronous Parathyroidectomy and Extended Thymectomy in Multiple Endocrine Neoplasia Type 1- a Case Report

Abstract In recent decades there has been a significant advancement in the management of neuroendocrine tumours (NETs) associated with multiple endocrine neoplasia type 1 (MEN-1). Hormone excess accounted for 75% of all MEN-1 deaths, however since the introduction of hormone blocking medication, deaths in patients with MEN-1 are now predominantly due to the malignant effects of the tumours. Half of all MEN-1 related deaths are due to tumours that are difficult to diagnose, including thymic NETs. Complete surgical resection is the mainstay of treatment for MEN-1 associated thymic NETs. The case patient was a 49-year-old male who was being investigated for a 3-month history of symptoms consistent with hypercalcaemia. Initially a chest X-ray demonstrated a large anterior mediastinal mass. Further imaging revealed parathyroid lesions and a calcified lesion in the uncinate process of the pancreas. This combination of symptoms and radiological evidence raised the possibility of MEN-1 as the diagnosis. The lesions were biopsy-proven atypical carcinoid NETs and the patient later underwent simultaneous neck dissection for bilateral subtotal parathyroidectomy and a midline sternotomy for total thymectomy of the large mediastinal mass. Further testing revealed the pancreatic mass was another primary tumour and the patient is scheduled for excision of this. In addition, the patient is also being treated with Lanreotide alongside chemotherapy. Mutation of the MEN-1 gene was later confirmed on genetic testing. Due to the increase in mortality from neuroendocrine malignancy, it is becoming ever more important to understand how to manage multiple NETs from a surgical perspective.

Intercostal nerve block is effective in open biopsies of the anterior mediastinal region: Case report and review.

Introduction and importanceAnterior mediastinal masses are rare conditions that can become symptomatic through compression of the airways and vascular structures. Fatal or severe complications can occur during anesthesia and surgery. With this review we aim to describe the state of the art in peri-anesthetic management of mediastinal tumors, which we illustrate with a clinical case.Presentation of caseWe report a case of a young female patient suffering from a large anterior mediastinal mass that underwent an open biopsy after intercostal nerve blocks (INB) in six consecutive right intercostal spaces (2nd to 7th). A right anterior mediastinotomy was performed and an excellent analgesic effect was achieved. The patient was awake and did not experience significant pain or cough, having received paracetamol 1 g and returned home later in the day. The diagnosis of non-Hodgkin's lymphoma was later confirmed.DiscussionOur review showed that anesthesia for mediastinal masses' resection or open biopsy is rare and prone to severe complications. Such complications are more important in children, patients in supine position, under general anesthesia and already symptomatic prior to the procedure. INB presents some advantages against paravertebral block (PVB) and thoracic epidural anesthesia (TEA), is easier to reproduce and has a shorter learning curve. Airway stenting with a rigid bronchoscope can be an alternative.ConclusionMultilevel medial axillary line INBs are safer and easier to reproduce than PVB, have less hemodynamic repercussion than TEA and can, therefore, be preferable for open anterior mediastinal biopsies or small masses resection.

Giant circulating malignant cells spotted in feathered edge of blood film.

A 20-year-old male presented with a 4-week history of dry cough, night sweats, weight loss, and fever. Blood tests showed normocytic anemia (hemoglobin 71 g/L) and severe thrombocytopenia (platelets 17 × 109/L). His blood film demonstrated leukoerythroblastosis, occasional red blood cell fragments, and giant cells in the feathered edge (Figure 1, panel A; Wright–Giemsa stain, original magnification ×400). Imaging revealed a large anterior mediastinal mass. Bone marrow biopsy revealed a hypercellular marrow with extensive involvement by high-grade malignant cells (Figure 1, panel B—aspirate; Wright–Giemsa stain, original magnification ×400; panel C—trephine biopsy; hematoxylin and eosin stain, original magnification ×200). Immunohistochemical staining only revealed CD43+, pankeratin+, and weak CD30 (Figure 1, panels D–F). The mediastinal mass was biopsied and showed similar results, as well as positivity for Sal-like protein 4 (SALL4; Figure 1, panel G) and epithelial membrane antigen (EMA). Serum alphafetoprotein was also elevated. Karyotype and metaphase Fluorescence In Situ Hybridization (FISH) from the bone marrow showed two isochromosome 12p (Figure 1, panels H–I). The final diagnosis was nonseminomatous germ cell tumor, not further classified. This case illustrates the importance of scanning the feathered edge of blood films to check for circulating metastatic cells. While often discussed in theory and seldom seen in practice, it is rare cases like this that reaffirm the importance of checking the feathered edge. We would like to thank Dr. Brian F. Skinnider, Anatomical Pathology at Vancouver General Hospital, for signing out the surgical report for the anterior mediastinal biopsy and arranging for the appropriate immunohistochemical stains. The authors declare no conflict of interest. Robert Guo and Tyler Smith helped sign out the hematopathology report on the bone marrow specimen for this case, as well as in writing and editing this manuscript.

Under Pressure: A Rare Case Of Right Ventricular Failure In Setting Of Large Mediastinal Mass

<h3>Introduction</h3> Large mediastinal tumors are rare and have a wide spectrum of presentations. Herein we present a case of right ventricular failure in the setting of a large anterior mediastinal chondrosarcoma. <h3>Case presentation</h3> 32 year old male with no known significant past medical history presented with one week of severe cough and chest pain. CT scan showed a large anterior mediastinal mass (9.3 × 12.4 × 13.6 cms), and biopsy was consistent with chondrosarcoma. Three weeks later, patient underwent complete surgical resection of mass along with partial chest wall, pericardium and diaphragm resection and reconstruction. Postoperative echocardiogram (TTE) showed severe right ventricular (RV) dysfunction and severe tricuspid regurgitation. Pulmonary Hypertension and Right heart failure service was consulted for further evaluation. <h3>Decision making</h3> Review of postoperative TTE showed no signs of pulmonary hypertension (systolic notching, septal flattening, RV hypertrophy). Review of preop TTE showed distal 2/3 of RV obscured by mediastinal mass and basal 1/3 RV hypokinetic. Review of chest CT from one month prior to surgery revealed large anterior mediastinal mass severely compressing distal third of RV along with significant right atrial enlargement. Two possible hypotheses for RV failure were contemplated at this point. 1. Chronic compression of right ventricle leading to severe geometric distortion/increased wall tension of non-compressed RV segments leading to myocardial dysfunction. 2. Acute surgical injury or chronic compression of right coronary artery leading to infarct and scar. Patient was diuresed and TTE done on postoperative day 5 showed significant improvement in RV size/function. Repeat TTE done on postoperative day 30 showed further improvement in RV size/function. These findings suggest direct myocardial compression as a more likely etiology of RV failure as opposed to infarct. <h3>Conclusion</h3> This case presents a rare case of large mediastinal mass causing right ventricular dysfunction by compression. This case also illustrates the importance of multimodality imaging (TTE and CT) in the evaluation of RV failure.

A large anterior mediastinal mass in a young infant

Abstract Funding Acknowledgements Type of funding sources: None. TITLE A large anterior mediastinal mass in a young infant Case Report A 4 week old male neonate, KS was referred to the emergency department with a 24 hour history of increased work of breathing, two brief episodes of apnoeas and inspiratory stridor. There was no infective symptoms or changes to his usual feeding pattern. There was no significant past medical history and he was on no regular medications. A chest x-ray demonstrated a large mediastinal mass and suspicion of cardiomegaly. A transthoracic echocardiogram demonstrated a structurally and functionally normal heart. However, there was a large anterior homogenous soft tissue mass extending to the left ventricular apex which was separate from the pericardium. This mass did not cause any heart chamber compression or compromise. Further cross-sectional imaging with cardiac computed tomography (CT) showed a non-enhancing uniform soft tissue mass occupying the superior and anterior mediastinum without evidence of calcification or fatty components. The lesion was seen to be extending from the root of the neck down to the left cardiac apex region with the total dimensions of the mass being 5.2 x 3.5 x 5cm. There was no compression of the great arteries or the airway. Parasternal ultrasound of the chest showed a starry sky appearance compatible with normal thymic tissue. Overall, the appearances were felt to be compatible with a prominent normal thymus. Discussion The differential diagnosis of an anterior mediastinal mass in young infants includes germ cell tumours (mainly teratomas), congenital thymic cysts and true thymic hyperplasia(1). These can be difficult to distinguish from the normal large neonatal thymus. The normal thymus can take on a variety of shapes and sizes and still be considered normal. One of the most important features of a normal thymus is the lack of mass effect or compression on the airway or vascular structures(2). True thymic hyperplasia is characterised by an increase in the size and shape of the thymus while preserving thymic architecture. If the anterior mass has a bipyramidal morphology with the presence of gross intercalated fat on CT, these findings are pathognomonic for thymic hyperplasia(3). Thymomas are rare in children and appear as well-defined, rounded or lobulated soft tissue density mass with mild enhancement on CT. It can demonstrate irregular borders with extension into adjacent structures and approximately 30% will have necrosis and internal cystic foci(4). The most common germ cell tumour in the mediastinum is a teratoma with the hallmark being fat, fluid and calcified components on CT(2). Lymphomas are the most common anterior mediastinal mass in children but are usually seen in children older than 5 years. They often cause mass effect with displacement of the trachea. CT scan demonstrates larger nodal areas with hypodense and cystic areas suggestive of necrosis(1). Abstract Figure 1 Abstract Figure 2

Management Consideration for Anterior Mediastinal Mass in a Patient With Grave's Disease.

A 36-year-old active duty female presented to an outside hospital emergency department for the evaluation of chest pain and weakness. Per report, comprehensive evaluation ruled out acute cardiopulmonary conditions. A computerized tomography scan revealed a large homogeneous anterior mediastinal mass. The patient was referred to a cardiothoracic surgeon who discussed treatment options, including surgery. She was subsequently referred to an interventional radiologist, who performed a biopsy. Findings were consistent with thymic hyperplasia without evidence of malignant cells. Follow-up with her primary care physician revealed an undetectable thyroid-stimulating hormone (TSH) level, and she was subsequently diagnosed with Graves' disease (GD). The primary care physician referred her to an endocrinologist who initiated treatment with methimazole. The patient's GD responded well to medication therapy; the thymic mass size decreased and her exercise tolerance increased. Notably, testing for TSH levels upon initial presentation could have avoided the need for biopsy.

Chylotamponade in Pediatric Primary Mediastinal Large B-Cell Lymphoma.

Chylotamponade involves rapid accumulation of chyle in the pericardium elevating the pericardial pressures above normal right heart filling pressures, and is extremely rare. A 12-y-old boy presented to the emergency with complaints of facial puffiness for 1 mo and breathing difficulty for 1 wk. The neck veins were distended, and the heart sounds were muffled. A chest CT demonstrated a large anterior mediastinal mass withpleural and pericardial effusions. Echocardiography confirmed cardiac tamponade. Pericardiocentesis revealed chylopericardium. He was placed on a chyle leak diet, and the drain was removed after 48 h. Biopsy of the mediastinal mass revealed a primary mediastinal B-cell lymphoma. He was successfully managed with chemotherapy. The index case demonstrates how prompt identification and management of chylotamponade and treatment of the underlying cause can lead to good clinical outcomes.

Surgery in large anterior mediastinal mass: case series of Hospital Kuala Lumpur

Surgery in large anterior mediastinal mass: case series of Hospital Kuala Lumpur

Transient maintenance of tracheal patency upon the insertion of a flexible bronchoscope in a patient with an anterior mediastinal mass: a case report

BackgroundPatients with an anterior mediastinal mass are at risk of perioperative respiratory collapse.Case presentationA 74-year-old woman with a large anterior mediastinal mass that led to partial tracheal collapse (shortest diameter, 1.3 mm) was scheduled for tracheobronchial balloon dilation and stent placement under general anesthesia. Although veno-venous extracorporeal membrane oxygenation (V-V ECMO) had been established, maximum flow was limited to 1.6 L/min, and general anesthesia induction was followed by hypoxia probably due to inadequate ventilation. A flexible bronchoscope was inserted through the tracheal lumen that was being compressed by the anterior mass; this not only increased tracheal patency but also enabled positive pressure ventilation and resulted in recovery from hypoxia. Scheduled procedures were successfully performed without complications.ConclusionWe describe a case wherein tracheal patency was transiently maintained by inserting a flexible bronchoscope in a patient with an anterior mediastinal mass.

Large Anterior Mediastinal Mass: Intraoperative Transesophageal Echocardiography Guided Evaluation and Management

The authors report a case of Large Anterior mediastinal mass in which Transoesophageal Echocardiography (TEE) revealed a large mass that was compressing the right atrium, SVC, henceforth, TEE helped in guiding aspiration and surgical resection of the cystic mass. Therefore, through this case report, authors emphasize the importance of performing intraoperative real-time TEE in the mediastinal mass. This imaging technique helps in visualizing the external compression of cardio-vascular structure and aid in their management, obviating the possibility of large vascular structures from being injured by the surgeon during intraoperative manipulation.

Unique Case of Mediastinal Teratoma with Unusual components

Mature teratoma is a benign, slow growing tumour. It usually affect adults in 20-40 years of age. Teratomas with mature pancreatic tissue are extremely rare. There are only a few cases of teratoma containing mature pancreatic tissue that have been reported in literature. Authors report a case of a 25-year-old male having a large solid cystic anterior mediastinal mass, which on excision, histologically revealed large areas of mature pancreatic tissue along with squamous epithelium with sebaceous glands and keratin, pseudostratified columnar ciliated epithelium, mucin secreting glands, cartilage, pigment and other germ cell derived mature elements. This is a unique case with unusual microscopic findings in the form of predominant pancreatic and also brain tissue along with other elements.

Malignant Psoas Syndrome Demonstrated by PET/CT in the Context of Metastatic Non Small Cell Lung Cancer

The significant cancer pain syndrome of malignant psoas syndrome (MPS), was first reported as a neurooncologic occurrence in 1990. The Syndrome is characterised by malignant infiltration of a psoas muscle, either directly or by involvement with haematogenously disseminated metastatic cancer. Direct involvement has been from primary tumours of the psoas muscle, or by extension from malignant paraaortic lymphadenopathy. Treatment is difficult, complex analgesia is essential, and benefits have been achieved from chemotherapy, radiotherapy and in select cases, surgery. Here, the case of a 60 year old female who presented with three months of moderate dyspnoea, low back and left inguinal region pain/numbness and lassitude, is reported. Chest radiograph and CT showed a large anterior mediastinal mass. FDG PET/CT revealed the mass to be intensely avid, with heterogeneous central areas of photopaenia. Avid lymphadenopathy was also present in two mediastinal nodal stations. Subdiaphragmatically, there was a metabolically FDG avid soft tissue mass in the superior part of the left psoas muscle, presumably accounting for her pain. There was no FDG avidity elsewhere. Core biopsy of the psoas mass revealed adenocarcinoma of probable lung origin. The patient responded symptomatically to intermediate dose radiation therapy. The pathophysiology of MPS is discussed and the range of cancer types associated with the Syndrome is updated.

Describing Treatment of Primary Mediastinal Large B Cell Lymphoma Using Rigorously Defined Molecular Classification: A Retrospective Analysis

Introduction Primary mediastinal large B cell lymphoma (PMBCL) is a rare non-Hodgkin lymphoma (NHL) with a female predominance; often presenting with a large anterior mediastinal mass. Though PMBCL has clinical and molecular features overlapping with Hodgkin lymphoma, it is a distinct entity defined by the World Health Organization classification. PMBCL is heterogeneously treated, and most patients receive front line therapy with either rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP) with radiotherapy (RT), or the more intensive etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin with rituximab (EPOCH-R) regimen. Diagnosis of PMBCL is made using clinicopathologic criteria and radiographic imaging, however gene expression profiling (GEP) studies reveal a characteristic genotypic signature distinct from diffuse large B cell lymphoma (DLBCL). Molecular classification of PMBCL using the Lymph3Cx assay from formalin-fixed paraffin-embedded tissue (FFPE) is feasible, reproducible, and highly concordant in a training and validation cohort (Mottok et al. Blood 2018). Using a multicenter cohort of patients, we sought to estimate the rate of mis-match among patients with a clinical diagnosis of PMBCL using Lymph3Cx, and describe treatment selections and outcomes for each group. Methods Patients were identified from a cohort of patients with newly diagnosed NHL from the University of Iowa and Mayo Clinic Molecular Epidemiology Resource, and the Lymphoma Epidemiology of Outcomes cohort. Patients were enrolled between 2002-2019, and included if they had clinically defined PMBCL. FFPE was retrieved from hematopathology archives of participating academic centers. All diagnoses of PMBCL were based on expert hematopathology review at the time of therapy, and all cases underwent classification by GEP using the Lymph3Cx assay. Lymph3Cx was performed in the clinical lab at the Mayo Clinic in Arizona: Contiguous unstained sections were deparaffinized and macrodissected to enrich for tumor content before RNA isolation;100-200 ng of total RNA was used in an nCounter Elements XT, hybridized, and processed the following day using the nCounter FLEX system. Raw counts were processed through the Lymph3Cx algorithm and results reported as probability of PMBCL (≥0.90 as PMBCL, ≤0.10 as DLBCL all other results "Unclear PMBCL/DLBCL") (A. Mottok et al, Blood, 2018). For cases classified as DLBCL, the Lymph2Cx cell-of-origin classifier results was reported (Scott et al, JCO, 2016). Time to event endpoints were described with Kaplan-Meier plots by groups defined by mismatch status and compared with a logrank test. Binary outcomes will be presented with 90% exact confidence intervals. Results Fifty patients were identified. Median age was 35 years (range 19-70). Sixty four percent were women. Median follow up was 47 months. Treatments included R-CHOP (44%), EPOCH-R (44%), and MACOP-B [methotrexate with leucovorin rescue, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin] (6%), other (4%). Ten patients (20%) had events (defined as progression or death). Three patients in the entire cohort (6%) died. The Kaplan-Meier estimated survival at 47 months (median follow-up) is 92%. The Lymph3Cx assay yielded gene expression data of sufficient quality in 47/50 cases (94%, 90% CI=85.2, 98.3%). Of 47 cases clinically identified as PMBCL, 5 unclear were DLBCL/PMBCL and 1 was Germinal Center B cell subtype of DLBCL. Among these 6 patients, 4 received R-EPOCH (66%), 1 received R-CHOP (16.6%). One patient had missing treatment data. One patient had an event requiring subsequent therapy; all patients remain alive. Conclusions Using 47 patients with PMBCL defined by histology, clinical and radiographic findings, and molecular features, we demonstrate high concordance between clinical phenotype and molecular genotype of PMBCL by Lymph3Cx. Among the 6 patients not classified as PMBCL, most received R-EPOCH. Differences in outcome by mis-match status await longer follow-up and further accrual of subjects to our data base. Our data suggest molecular genotyping may have a role in mediastinal presentations of large cell lymphoma to optimize treatment decision making. Disclosures Maurer: Nanostring: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Celgene / BMS: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; Kite: Membership on an entity's Board of Directors or advisory committees. Cerhan:BMS/Celgene: Research Funding; NanoString: Research Funding. Flowers:AbbVie: Consultancy, Research Funding; Kite: Research Funding; Burroughs Wellcome Fund: Research Funding; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy, Research Funding; Denovo Biopharma: Consultancy; Celgene: Consultancy, Research Funding; Cancer Prevention and Research Institute of Texas: Research Funding; TG Therapeutics: Research Funding; Eastern Cooperative Oncology Group: Research Funding; V Foundation: Research Funding; Bayer: Consultancy; National Cancer Institute: Research Funding; Millennium/Takeda: Consultancy, Research Funding; Gilead: Consultancy, Research Funding; Acerta: Research Funding; Spectrum: Consultancy; Pharmacyclics/Janssen: Consultancy; Karyopharm: Consultancy; OptumRx: Consultancy; Leukemia and Lymphoma Society: Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy. Friedberg:Acerta Pharma - A member of the AstraZeneca Group, Bayer HealthCare Pharmaceuticals.: Other; Astellas: Consultancy; Bayer: Consultancy; Kite Pharmaceuticals: Research Funding; Portola Pharmaceuticals: Consultancy; Roche: Other: Travel expenses; Seattle Genetics: Research Funding.

PRIMARY MEDIASTINAL SEMINOMA FOUND ON EVALUATION FOR WEIGHT LOSS

SESSION TITLE: Medical Student/Resident Disorders of the Mediastinum Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Extragonadal germ cell tumors (GCTs) typically arise in midline locations such as mediastinum and retroperitoneum. They are formed either due to failure of primordial germ cells to migrate to the gonadal ridges [1] or reverse migration of the transformed germ cells in the testes [2]. Mediastinal seminomas are rare tumors constituting about 1/3rd of malignant mediastinal GCTs and 2-4 percent of mediastinal masses [3]. CASE PRESENTATION: A 55-year-old man with a history of active smoking (½ pack cigarettes per day), hepatitis C, bipolar disorder, prior alcohol/intravenous drug use (heroin and cocaine) presented with shortness of breath and 50-pound weight loss. Chest computed tomography (CT) revealed a 3.0 x 1.1 cm para-aortic lymph node. Positron emission tomography (PET/CT) scan showed hypermetabolic activity (maximum standardized uptake value of 10). Bronchoscopy with EBUS (endoscopic ultrasound) and mediastinoscopy were considered as methods to obtain tissue but discarded due to the location of the mass. He underwent a left Video-assisted thoracoscopic surgery (VATS) which showed seminoma. H&E (hematoxylin and eosin) slides revealed pale tumor cells with distinct nuclei and prominent central nucleoli in a background of lymphocytic infiltrate. The tumor cells stained positive for germ cell markers CD117, Oct 3/4 and Sall 4; but were negative for melanoma markers (Mart1a, S100), as well as CK20, CK7, Pancytokeratin, CD30, CD15, TTF1 and CDX2. DISCUSSION: Mediastinal seminomas occur mainly in men aged 20 to 40 years. They are typically slow growing and can be very bulky by the time they cause symptoms. Serum beta subunit of human chorionic gonadotropin (beta-hCG) is elevated in approximately one-third of patients. They do not produce alpha-fetoprotein (AFP). Ultrasound is advised in all cases to evaluate for any testicular primary. Seminomas are exquisitely sensitive to both cisplatin-based chemotherapy and radiotherapy (RT) but local control with surgery and RT only have modest success due to their typically later presentation. The commonly used chemotherapy regimens are 3 cycles of bleomycin/etoposide/cisplatin (BEP) or 4 cycles of etoposide/cisplatin (EP) (in patients who have previously received RT, who have underlying lung disease or age more than 50 years to avoid bleomycin lung toxicity). Long-term disease-free survival is achieved in roughly 90 percent of patients treated with chemotherapy. CONCLUSIONS: Primary mediastinal seminoma is a malignant extragonadal GCT most commonly found in the anterior mediastinum. Usually, young men in their 20-40s present with large 4-11cm anterior mediastinal masses which cause symptoms by compressing local structures. Or, as in our case, they are found incidentally. Surgery/RT can be considered but many patients present late so local control is not possible. However, these tumors respond well to chemotherapy with complete response rates of 90% Reference #1: Intracranial germ cell tumors: a comprehensive review of proposed embryologic derivation; Glenn OA, Barkovich AJ; Pediatr Neurosurg. 1996;24(5):242; PMID 8933567 Reference #2: Genetics and biology of adult human male germ cell tumors; Chaganti RS, Houldsworth J; Cancer Res. 2000;60(6):1475; PMID 10749107 Reference #3: Primary germ cell tumors of the mediastinum: II. Mediastinal seminomas--a clinicopathologic and immunohistochemical study of 120 cases; Moran CA, Suster S, Przygodzki RM, Koss MN; Cancer. 1997;80(4):691; PMID 9264352 DISCLOSURES: No relevant relationships by William Han, source=Web Response No relevant relationships by Sahib Singh, source=Web Response