Case Of Thymoma Research Articles

Lifesaving surgery for a ruptured invasive thymoma using the hemi-clamshell approach: a case report

BackgroundAmong anterior mediastinal tumors, a teratoma is known to rupture with growth, but there have been few previous reports about thymoma rupture. We here report a rare case of an invasive thymoma with intrapulmonary and intrathoracic rupture requiring emergency life-saving surgery. To our knowledge, this is the first such case in the literature.Case presentationA 56-year-old woman suddenly experienced right precordial pain and hemoptysis. Enhanced computed tomography revealed a large mediastinal tumor pressing against the pulmonary hilar vascularity, with extravasation of blood into the right lung. Tumor rupture into the lungs was suspected. Given the deterioration of her respiratory status and hemodynamics, thymomectomy with removal of the involved tissues was urgently performed using the hemi-clamshell approach and intrapericardial dissection, with veno-arterial extracorporeal membrane oxygenation on standby. She survived, and no recurrence has been noted for 2 years postoperatively.ConclusionsA large thymoma can suddenly rupture into the thorax, similar to the rupture of a teratoma. Additionally, in cases with hemoptysis, an appropriate procedure should be selected to reach both the pulmonary hilum and thorax for complete resection, as hemoptysis might suggest tumor invasion into the lungs.

Resected case of giant cystic thymoma with spontaneous intracystic hemorrhage

BackgroundSpontaneous intracystic hemorrhage of cystic thymoma is very rare. We encountered a patient with giant cystic thymoma with spontaneous intracystic hemorrhage and successfully resected the thymoma.Case presentationA 38-year-old man was referred to our hospital with chest pain. Computed tomography revealed a uniform anterior mediastinum cystic mass. Two days after hospitalization, his chest pain worsened. Subsequent computed tomography showed that the tumor had become inhomogeneous. The patient’s symptoms gradually improved over a fortnight, and surgery was performed. The tumor was a cystic mass with a thick fibrous capsule filled with hemorrhagic necrotic tissue and was diagnosed as a cystic thymoma.ConclusionsMediastinal cystic lesion with expansion or contrasting effects in the wall may be a cystic thymoma, and it has the possibility of hemorrhaging in the cyst. In such a case, surgical resection is recommended.

Pre and post-extended thymectomy plasmapheresis accelerates mechanical ventilation extubation in Myasthenia Gravis patients with Thymoma

Background: Myastenia gravis (MG) is a neuromuscular junction disorder that causes significant disability in the patient. Plasmaparesis and thymectomy are some therapeutic modalities in MG patients. Patients with MG of 10-15% had thymoma and 60% occurred thymic hyperplasia. Thymectomy may improve MG outcomes in 54-94% of patients (thymoma cases) or 21-42% of patients (cases of thymic hyperplasia). Plasmaparesis perioperatif still controversial. Case report: The 60-year-old man comes with a complaint both eyelids often close and both hands and feet experience fluctuating weakness, improved at rest. Patients with a history of DM and pulmonary TB. On the physical examination obtained eyelid twitch response and improved ptosis on ice test. Laboratory shows hyperglycemia and thrombocytopenia. Electrophysiological examination supports neuromuscular junction lesions. In thoracic and thoracic rectal images the mediastinal mass was obtained. Patients were diagnosed with myastenia gravis with suspected thyroid mediastinal mass. Treatment given mestinon 60 mg every 8 hours peroral, thymectomy plan, platelet transfusion, and plasmaparesis. Obtained a tumor with a large 10x8x7 cm with adhesions around the organ. Microscopic features support a thymoma A. Patients receive perioperative plasmaparesis 1 series (5x administration) divided, 2 preoperative and 3 postoperative times. The patient used mechanical ventilation for less than 24 hours and no residual symptoms. Conclusion: Myastenia gravis grade IIa (Osserman) with thymoma A performed extended thymectomy. Plasmaparesis given pre and post surgery showed clinical improvement and duration of short ventilator use. Good prognosis associated with mild MG degree, no myastenia crisis. Keywords: myastenia gravis, thymectomy, plasmaparesis

Image-guided Fine Needle Aspiration Cytology of Intrathoracic Lesions.

Background:Percutaneous, image-guided transthoracic fine needle aspiration cytology (TTFNAC) is a rapid, yet accurate, and well-established diagnostic method used in the cytological evaluation of intrathoracic lesions. The study was done to determine the utility of image-guided TTFNAC in diagnosis of intrathoracic lesions.Subjects and Methods:A retrospective analysis of all cases who underwent image-guided TTFNAC of a suspected intrathoracic lesion, in a tertiary care hospital was done over a period of 3 years.Results:During the study period, 124 cases of image-guided FNAC of intrathoracic lesions were obtained. The mean age at presentation was 60.5 years with M:F: 3.6:1. Neoplastic lesions (71.5%) outnumbered the nonneoplastic lesions (28.5%). The most common tumor was adenocarcinoma (25%) followed by squamous cell carcinoma (SCC, 11%), and small cell carcinoma (5%). There was one case each of anaplastic carcinoma, plasmacytoma, bronchoalveolar carcinoma, and non-Hodgkin lymphoma (NHL). Most of the lesions were found on the right side and upper lobe. Among the mediastinal lesions, we found two cases of thymoma and one case each of NHL)/primitive neuroectodermal tumor (PNET), NHL, and small cell carcinoma metastasis to lymph node followed by ten cases of inflammatory lesions and seven cases of tuberculosis (TB).Conclusion:Image-guided TTFNAC of intrathoracic lesions is a safe method when done by well-trained medical personnel with lesser rate of complications. An early accurate diagnosis of malignancy can be made based on the cytological features; however, further subtyping of the malignancy may sometimes be difficult due to overlapping cytological features. TTFNAC can be a diagnostic tool for identifying nonneoplastic lesion such as TB. Hence, image-guided FNAC aids in early diagnosis and management of patients with intrathoracic lesions.

Ectopic Thymoma of the Right Atrium: A Case Report

Abstract Ectopic thymoma arising in organs other than the thymus is rare. To date, there is no report of intracardiac ectopic thymoma in the English language literature. We report a rare case of a right atrial ectopic thymoma. A 61-year-old woman presented with puffiness of face and shortness of breath. Cardiac computed tomography revealed a large right atrial mass with near-total occlusion of the chamber and extension into the superior vena cava and inflow tract of the right ventricle. She underwent resection of the right atrial mass. The final pathological diagnosis was intracardiac ectopic thymoma.

Changes in speech charactersitics post thymoma

<p class="abstract">Thymomas are rare tumors of the anterior mediastinum that may be benign or malignant. Thymomas are frequently associated with neuromuscular disorders like myasthenia gravis. Multiple cranial nerves are involved which may affect speech of the patients. Flaccid dysarthria is one of the common motor speech disorders associated with thymoma. Other characteristics may include decrease of intelligibility, reduced vocal stamina, reduction of emotional expressivity etc. The present case study illustrates changes in speech characteristics in a 35 year old male patient with thymoma associated with myasthenia gravis. Detailed speech assessment was done which revealed deviant speech patterns like vocal tremors, decreased loudness, hypernasality etc. The aim of the study was to document speech characteristics in a known case of thymoma associated with myasthenia gravis.</p>

P3.CR-31 A Case of Thymoma with Autoimmune Hepatitis Following Preoperative Chemotherapy

We encountered a case of thymoma with autoimmune hepatitis. A 63-year-old woman was found to have an abnormal finding on chest radiography during a medical checkup, but did not seek further care. She was referred to our hospital one year later when a bilateral hilar abnormality was again found during a checkup. Chest computed tomography (CT) showed a 4.6 × 3.0 × 5.6 cm mass with calcifications in the anterior mediastinum. The tumor invaded the right lung and middle lobe, in association with a 2.0-cm daughter nodule in the head of the main tumor, with multiple pleural seeding lesions in the right thoracic cavity. Although she was asymptomatic, the anti-acetylcholine receptor antibody level was elevated to 33 nmol/L and the soluble IL-2 receptor antibody was elevated to 1,700 U/mL. The mass was diagnosed with CT-guided biopsy as a type-B2 thymic tumor (cT3N0M1a, c-Stage IV). She underwent induction chemotherapy (ADOC, 2 courses). After chemotherapy, abnormal liver enzyme levels (aspartate aminotransferase: 451 U/L, alanine aminotransferase: 529 U/L) were noted on preoperative examination. She was diagnosed with autoimmune hepatitis based on liver biopsy findings and treated with oral prednisolone 30 mg. Surgery was performed after prednisolone dose was gradually decreased to 20 mg. Extended thymectomy and pulmonary wedge resection using median sternotomy were performed. Pleural dissemination was resected using video-assisted thoracoscopic surgery. The pathological findings showed type-B3 thymic carcinoma (pT3N0M1a, p-Stage IV, Masaoka classification IVa). She was placed under observation without any additional treatment. Prednisolone dose has been gradually decreased to 15 mg without exacerbation of liver function. The anti-acetylcholine receptor antibody level decreased after surgery. Autoimmune diseases in association with thymoma are well known, but reports of autoimmune hepatitis are very rare. Autoimmune hepatitis must be considered when acute liver damage is observed.

Thymomas With a Prominent Alveolar Growth Pattern: A Clinicopathologic and Immunohistochemical Study of 12 Cases.

Twelve cases of thymomas with prominent alveolar-like growth pattern are presented. The 12 cases were identified during a review of more than 350 cases of thymomas. The patients were five women and seven men between the ages of 48 and 69 years (mean, 58.5 years). Clinically, all patients presented with nonspecific symptoms. Grossly the tumors varied in size from 3.5 to 5 cm in greatest diameter. Histologically, all tumors showed a predominant alveolar-like growth pattern without a significant lymphocytic component. Immunohistochemistry showed positive staining for pan-keratin, keratin 5/6, and p63. Clinical follow-up showed that nine patients have remained alive and well with no recurrence, while no follow-up was obtained in three patients. The cases herein described highlight the spectrum of growth patterns that thymomas may show and also highlight the importance to keep thymomas in the differential diagnosis of tumor with prominent alveolar-like growth pattern.

Thymic epithelial neoplasms with rhabdomyomatous component: a clinicopathological and immunohistochemical study of 7 cases

Seven primary thymic epithelial neoplasms, 3 thymomas and 4 thymic carcinomas, with rhabdomyomatous component are herein described. The patients are 2 women and 5 men between the ages of 42 and 62 years (average, 52 years). Clinically, the patients presented with nonspecific symptoms of cough, chest pain, and dyspnea. None of the patients had history of myasthenia gravis or of previous malignancy. Diagnostic imaging revealed the presence of an anterior mediastinal mass in all the patients. Surgical resection was accomplished in all the cases. The 3 thymoma cases were encapsulated tumors: histologically, 2 were lymphocyte rich (World Health Organization type B1), and 1 was an atypical thymoma (World Health Organization type B3). All the thymic carcinomas were ill-defined tumor masses with infiltrative borders and histologically were high-grade carcinomas. In each tumor, in different proportion, there were easily identifiable areas with rhabdomyomatous component characterized by larger cells with eosinophilic cytoplasm and eccentrically placed nuclei. Immunohistochemical stains in all cases showed clearly demarcated presence of the epithelial component (keratin positive/desmin and myoglobin negative) and the rhabdomyomatous component (desmin and myoglobin positive/keratin negative). The 3 patients with thymoma are alive and without recurrence 3 and 5 years after surgical resection, whereas 3 patients with carcinoma died between 2 and 3 years after surgical resection. One patient with thymic carcinoma was lost to follow-up. The current cases highlight the ubiquitous distribution of myoid cells in different types of thymic epithelial neoplasms.

Progressive peripheral CD8+ T lymphocytosis complicated by pure red cell aplasia following immunosuppressive therapy for thymoma-associated myasthenia gravis

We herein report a unique case of type B2 thymoma-associated myasthenia gravis which was ameliorated by immunosuppressive therapy in combination with chemotherapy. However, the patient subsequently developed pure red cell aplasia and marked lymphocytosis after additional chemotherapy aimed at improvement of thymoma. While a separate immunosuppressive regimen was effective for anemia, lymphocytosis was exacerbated. The biopsied thymoma specimen contained CD4+, CD8+, and CD4+/CD8+ T cells, some of which were CD3−, suggesting immature thymocytes. In contrast, majority of the peripheral lymphocytes were polyclonal CD3+/CD8+/T cell receptor (TCR)αβ+ T cells. The CD4/CD8 ratio in the present patient might be affected by immunosuppressive agents, resulting in CD8+ T cell expansion associated with pure red cell aplasia. Although several cases of thymoma accompanied by peripheral T cell lymphocytosis were reported, marked CD8+ T cell proliferation is extremely rare.

Canine Thymoma Associated to Myasthenia Gravis

Background: Thymomas are epithelial neoplasms of the thymus, although lymphocyte infiltration is common. Histological features are not sufficient to define its biological behaviour, which is dependent of clinical criteria of invasiveness and resectability. Myasthenia gravis may happen as a paraneoplastic syndrome in up to 47% of canine thymomas. Thisarticle aims at reporting a case of thymoma associated with myasthenia gravis in a dog, emphasizing the morphological, phenotypical and therapeutical aspects.Case: A 7-year-old, male Labrador, was presented with a history of acute dyspnea and exercise intolerance. The physical examination revealed a “red-brick” mucousa, tachycardia and cardiac and pulmonar hypofonese. Chest radiographs revealed an area of increased radiopacity in the cranial mediastinum without a plane of separation to the heart. The eccodopplercardiogram exam identified a poorly delimited mass adjacent to the base of the heart, measuring 9.5x6.8cm. Computed tomographydemonstrated it as an expansive neoformation (9.5x6.5x7.8cm). Mass was removed through intercostal thoracotomy and the removed tissue was submitted to histopathology with a diagnosis compatible with type AB thymoma (mixed). Immunohistochemistry was positive for AE1/AE3 citokeratin in 90% of epithelial cells, confirming tumour origin. Tumour infiltrating lymphocytes were positive for CD79a (70%) and CD3 (20%). The proliferation index (Ki-67 imunolabeling) was 60%. About 45 days after surgery the patient was presented with generalized muscle weakness and regurgitation, with confirmed megaesophagus on chest X-ray. Treatment with pyridostigmine was initiated because of suspected myasthenia gravis, and complete remission of the neurological signs occurred within a month. A chemotherapeutic protocol with carboplatin wasthen instituted. After four sessions, a new thoracic radiograph revealed tumour recurrence in the cranial mediastinum. Therefore, metronomic chemotherapy was started sequentially with oral chlorambucil and firocoxib. Patient remained well for nine months when regurgitation and muscle weakness re-initiated, even with pyridostigmine treatment. New chestX-ray demonstrated increased tumour mass and the owner decided for euthanasia, resulting in a survival time of 368 days.Discussion: The prognosis of the thymoma depends on the histological type, clinical staging and presence of paraneoplastic syndromes. Due to the heterogeneity of the cases, there are not enough studies available to compare the animals submitted to different therapeutic modalities. In humans, when possible, and in the absence of metastases, complete surgical resection is the standard treatment followed by chemotherapy and/or adjuvant radiotherapy. In dogs, surgical resection of thymomasshould be considered, despite the invasiveness detected in imaging studies. The presence of paraneoplastic syndromes, such as myasthenia gravis, are commonly associated with worse prognosis, however, as evidenced in this case, pyridostigmine was useful in maintaining the neuromuscular function and patient´s quality of life, along with surgery and adjuvant chemotherapy, which probably contributed to the increase of the expectation of life. Further studies are necessary to evaluate the efficacy of adjuvant chemotherapy in maximum tolerated and metronomic dosage, for thymic neoplasms in dogs.Keywords: thymus, neoplasia, paraneoplastic syndrome, carboplatin, cyclophosphamide.

Thymoma and thymic carcinoma associated with multilocular thymic cyst: a clinicopathologic analysis of 18 cases

BackgroundMultilocular thymic cysts (MTCs) associated with thymomas or thymic carcinomas (TCs) are rare and may be misdiagnosed as other benign cystic lesions.MethodsWe retrospectively analysed 18 cases of thymomas or TCs associated with MTCs, which were retrieved from 309 consecutive patients with thymomas or TCs in the Chinese population, emphasizing clinicopathologic characteristics, immunophenotypes and the prognostic impact.ResultsA total of 14 tumours were described as cystic or solid-cystic masses, and the other 4 tumours were described as solid masses. Histologically, 2 atypical type A, 2 type AB, 1 type B1, 8 type B2, 1 type B3, 1 microscopic thymoma (type A), 2 squamous cell carcinomas (SCCs) and 1 lymphoepithelioma-like carcinoma (LELC) were classified. Prominent multilocular cystic areas with chronic inflammation were observed. The follow-up ranged from 2 to 79 months. Sixteen patients survived without any evidence of recurrence after complete resection.ConclusionsOur study suggests that thymomas or TCs associated with MTCs are rare in the Chinese population and have a better clinical behaviour than thymomas or TCs without MTCs. Our data also expand the histologic spectrum of thymomas or TCs accompanied by MTC. To our knowledge, this is the first report of atypical type A thymoma and LELC associated with MTCs.

Long-term survival after R0 resection of thymoma

Background The aim of this study was to evaluate the results of R0 resection of thymoma to identify prognostic factors for long-term outcomes. Methods Data of 62 patients (28 male, 34 female) with a mean age of 47.26 ± 14.42 years, who underwent R0 resection for thymoma and were followed-up between February 2004 and March 2016, were analyzed retrospectively. Results Eight patients had a video-assisted thoracoscopic thymectomy and 54 had a transsternal extended thymectomy. During a mean follow-up of 128.67 ± 7.95 months, regional recurrence of thymoma was observed in 9 (14.5%) patients. Overall 5- and 10-year survival rates were 85.36% and 78.20%, respectively. The 5- and 10-year survival rates in patients aged < 50 years were significantly better than in those aged ≥ 50 years (92% and 72% vs. 88% and 39%, p < 0.0001). The 10-year overall survival of patients in Masaoka stage I and II was better than those in stage III (88.9%, 78.4%, 69.8%, respectively, log-rank p < 0.001). The 10-year survival of patients with World Health Organization histological type A, AB, and B1 thymomas was better than those with type B2 and B3 (log-rank test p < 0.001). In multivariate analysis, age < 50 years ( p = 0.001), Masaoka stage ( p = 0.006), histological type ( p = 0.001), and recurrence ( p = 0.04) were independent prognostic factors for survival. Conclusion Our study indicates that age < 50 years, Masaoka stage, histological type, and recurrence are the determinants of survival in surgically resected cases of thymoma.

Research Highlight: Metastatic Malignant Thymoma to the Abdomen

Thymoma is a rare neoplasm of thymic epithetical cells that has the ability to spread by local extension. While metastases are most commonly confined to the pleura, pericardium and diaphragm, cases of abdominal metastases have been reported. In a recent publication [ref 7], we conducted a SEER database and literature review to identify cases of malignant thymoma (MT) and abdominal metastases, demonstrating an increasing overall incidence of MT with a significant male predominance. Additionally, we suggested routine screening for all MT patients as roughly 50% of abdominal metastasis cases presented as asymptomatic, as well as a multimodal treatment approach for those with metastatic MT to the abdomen. In this highlight, we briefly present the evidence for a rising rate of MT, review reported cases of abdominal metastasis, and emphasize the need for a multimodal treatment approach.

Correlation of blood concentration with efficacy and safety of tacrolimus in treatment of myasthenia gravis patients

Objective To investigate the relationship of blood concentration of tacrolimus with efficacy and safety in treatment of patients with myasthenia gravis. Methods The clinical data of 74 patients with myasthenia gravis admitted in our hospital from January 2013 to December 2015 were analyzed retrospectively. The blood concentrations of tacrolimus were determined by chemiluminescence microparticle immunoassay. Treatment effects were evaluated with clinical relative scoring in China. Results There were 41 men and 33 women in 74 patients with the mean age of (56.7±15.8) years. According to the Osserman classification, there were 7 cases of type Ⅰ, 18 cases of type Ⅱb, 27 cases of type Ⅱa, 5 cases of type Ⅲ and 17 cases of type Ⅳ. Forty seven patients underwent thymectomy, including 9 cases of thymoma and 38 cases of hyperplasia. Patients were followed up for (28.1±14.5)days, and the effective rate was 74 %(55/74). There was no significant correlation between tacrolimus blood concentration and clinical efficacy. The incidence of adverse reaction of tacrolimus was 22%(16/74), and the incidence of adverse reactions increased with the increase of blood concentration. Conclusion Tacrolimus is effective in treatment of myasthenia gravis. The correlation of blood concentration of tacrolimus with the clinical efficacy needs to be further studied, but certainly, the monitoring of blood concentration can reduce the incidence of adverse reactions. Key words: Myasthenia gravis; Tacrolimus; Drug monitoring; Adverse drug reaction

S52. A case of myasthenia gravis related to use of pembrolizumab

Pembrolizumab is an immune checkpoint inhibitor and a monoclonal antibody which inhibits the programmed cell death 1 (PD-1) receptor. Immune checkpoint inhibitors have specific side effects known as “immune-related adverse events”. Most common ones are dermatologic, endocrine, gastrointestinal and hepatic events. Complications related to immune checkpoint inhibitors such as encephalitis, transverse myelitis, immune neuropathies, myositis and myasthenia gravis (MG) are reported to be 5%. We present a malign thymoma case that developed myasthenia gravis during treatment with pembrolizumab. 57 year-old-male patient came to the clinic with complaints of diplopia, drooping eyelids, difficulty with talking and swallowing. His medical history included carrier state for Hepatitis B with previous tenofovir use. He was diagnosed with thymoma in 2011 during an asymptomatic routine medical screening. After the metastasis of disease, he received radiotherapy and chemotherapy (3 cures of Taxol and Carboplatin) in 2015. He was started on pembrolizumab in 2017 during an asymptomatic period. Right after the 2nd dose of pembrolizumab and 1 month after the beginning of therapy, he came to our clinic with ocular and bulbar symptoms: double vision, drooping eyelids, difficulty with talking and swallowing. Upon performing single fiber Electromyography, we detected neuromuscular junction dysfunction and diagnosed the patient as MG. The patient was given 170gr IVIG and methylprednisolone 96 mg/day sequentially. Acetylcholine receptor (AchR) and anti-MUSC antibodies were negative. In time, his bulbar symptoms ameliorated and the patient was followed under the treatment of methylprednisolone and pyridostigmine. Use of pembrolizumab for thymic cancers has not been reported previously. The occurrence of MG due to pembrolizumab is comparatively rare; if it occurs, however, immune side effects appearing due to these treatments are less responsive to immunosuppressant and immunomodulator treatments. Because our patient had thymoma as the targeted malignancy, it was hard to decide whether it was the thymoma or the pembrolizumab causing the emergence of MG. Seeing symptoms right after pembrolizumab treatment along with 6 years of stable course of the disease pushed us to think MG as “an immune-related adverse event”. Nevertheless, thymoma may have facilitated this adverse event. Long-term data on undesirable immune effects of new checkpoint inhibitors is lacking. For this reason, clinicians should approach cautiously to possible exacerbations of autoimmune diseases and related risks.

Ectopic thymoma in the paratracheal region of the middle mediastinum: a rare case report and literature review

BackgroundThymomas generally arise from the thymus in the anterior mediastinum. Ectopic thymomas arising in the middle mediastinum are rare. We present a case of a thymoma arising from the ectopic thymic tissue in the right paratracheal region.Case presentationThe patient was a 67-year-old male who underwent an enhanced-computed tomography examination as preoperative staging for colon cancer. A 20-mm nodule in the right paratracheal region was found incidentally. Fluorodeoxyglucose (FDG) accumulation was detected in this solitary nodule by FDG-positron emission tomography, mimicking an enlarged, possibly malignant lymph node. The tumor was removed by thoracoscopic surgery, and a postoperative pathological diagnosis of type AB thymoma was made. Foci of ectopic thymic tissues were found adjacent to the thymoma. The patient was disease-free and without recurrence 2 years postoperatively.ConclusionsIncluding the present case, 13 cases of ectopic paratracheal thymoma have been reported in the English literature, all of which were found on the right side of the paratracheal region. Although ectopic thymomas in the paratracheal region are rare, thymomas may be considered as a differential diagnosis for a paratracheal nodule.

World Health Organization type B2 thymoma with an abundance of Hassall's corpuscles: A case report.

Hassall's corpuscles (HCs) are characteristic components of the medulla of the mammalian thymus and thymoma with an abundance of HCs is even more rare, with only five cases having been reported in the literature, to the best of our knowledge. Furthermore, their morphology usually resembles World Health Organization (WHO) type B2 or B3 thymoma. The biological behavior appears indolent and is rarely associated with myasthenia gravis. However, whether it is a separate entity or a variant of organotypical thymoma WHO B2 or B3 remains to be elucidated. The present case report reports a type B2 thymoma with a large presence of HCs from a 58-year-old Chinese woman, and investigates its histopathological characteristics, immunological features and biological behavior. Notably, the present case appeared biologically more aggressive compared with the cases reported previously. The aim of describing this rare case of thymoma with an abundance of HCs is so that it can be recognized and classified by pathologists.

PD-L1 immuno-expression assay in thymomas: Study of 84 cases and review of literature

Programmed death ligand 1 (PD-L1), an immune check point inhibitor, is known to be expressed in several malignancies and is being considered as a prognostic factor and a potential immunotherapeutic target. The aim of this study was to characterize PD-L1 expression in thymomas and to determine correlation with clinicopathological features and previously published studies in the literature. Tissue microarrays were prepared from selected blocks of thymomas and immunohistochemistry (IHC) for PD-L1 was performed. Cases were considered as PD-L1 positive or negative depending on whether the percentage of stained thymic epithelial cells were <25 or >25%. Results were compared clinically and with previously published studies using Google and Pubmed search engines. Of 84 cases of thymoma, 69 (82.1%) revealed PD-L1 positivity in >25% cells. 94.23% of type B thymoma subtypes (B1/B2/B3) were PD-L1 positive (P < 0.001). There was no correlation of PD-L1 with age, gender, myasthenia gravis, the tumor size or stage of disease. Nine studies were available in the literature; most of which showed PD-L1 expression in higher stage and B subtype however percentage positivity varied from 53.7% to over 90%. PD-L1 expression is frequent in type B (B1/B2/B3) thymomas. It can be easily evaluated by IHC even on small biopsies in unresectable cases, thereby enabling improved clinical evaluation as well as prognostic stratification of patients. It will serve as a potential indicator for benefit from anti-PD-L1 antibody immunotherapy in thymomas.

多中心性発生と考えられた同時多発胸腺腫の1切除例

症例は69歳，女性．左乳癌に対する乳房切除術の既往あり．乳癌術前より胸部CTで24 mmと8 mmの2つの前縦隔腫瘍を認めた．筋無力症状は認めず，抗アセチルコリンレセプター抗体は陰性であった．5年の経過で，ともに増大傾向を認めたため手術の方針とした．右側アプローチで胸腔鏡下胸腺部分切除術を施行した．縦隔右側に存在した腫瘍は53 mmのtype B1，正岡病期分類II期の胸腺腫，左側は20 mmのmicronodular thymoma with lymphoid stroma，正岡病期分類II期と診断した．これは組織型が異なるため，多中心性発生の同時多発胸腺腫と考えられた．同時多発胸腺腫は稀な疾患であり，その頻度は切除例の2.2%以下と報告されている．胸腺腫は多中心性発生もしくは胸腺内転移の可能性を有しているため，術前より副病変の存在に留意し画像診断を慎重に行い，切除範囲を決定すべきである．