Benign lesions of the mediastinum.

Mediastinal tumours represent a heterogeneous group of entities derived from the manifold structures located in or adjacent to the mediastinum. Due to the occurrence of some of these tumours in characteristic mediastinal compartments, an anatomical subdivision of the mediastinum in the prevascular (anterior), visceral (middle), and paravertebral (posterior) is helpful for the differential diagnosis. Benign anterior mediastinal tumours linked to an enlargement of the thymic gland mainly consist of thymic cysts and several types of thymic hyperplasia: true thymic hyperplasia, rebound hyperplasia, lymphofollicular hyperplasia, and so-called thymic hyperplasia with lymphoepithelial sialadenitis (LESA)-like features. Mature teratomas, ectopic (para)thyroid tissue, and benign thymic tumours such as thymolipoma or thymofibrolipoma represent further typical tumours of the anterior mediastinum. Pericardial, bronchogenic, or oesophageal duplication cysts predominate in the middle mediastinum, whereas neurogenic tumours and myelolipomas are characteristic findings in the posterior compartment. Vascular tumours, lipomas, adenomatoid tumours, Castleman disease, or mediastinitis are further examples of less frequent tumours or tumorous lesions affecting the mediastinum. This review focuses on benign mediastinal lesions with an emphasis on benign tumours of the thymus. Besides histology, characteristic epidemiological and clinical aspects prerequisite for the correct diagnosis and patient management are discussed.

Unusual onset of Graves' disease associated with thymic hyperplasia in a 5-year-old girl with congenital bilateral clinical anophthalmia: diagnostic and therapeutic challenges.

OBJECTIVES: Graves' disease (GD) is a rare auto-immune disorder in pediatric population. The association between GD and thymic hyperplasia was rarely reported in children. Diagnosis and management of GD are challenging in children. CASE PRESENTATION: This report presents the case of a 5-year-old girl with a personal history of asthma and congenital bilateral isolated clinical anophthalmia who presented with acute congestive heart failure, sinus tachycardia and atypical signs of orbitopathy with edema and erythema of the lower right eyelid and excessive tearing. The diagnosis of GD was based on detecting a suppression of serum TSH level and the presence of high titers of TRAbs. Relapse occurred after 10 months of antithyroid drugs with chief complaints of palpitations, dyspnea and dysphagia. Computed tomography showed heterogeneous anterior mediastinal mass with no invasion into the surrounding tissue. The marked shrinkage of the mass after radioiodine therapy supported the diagnosis of thymic hyperplasia associated with GD. CONCLUSIONS: The presence of clinical anophthalmia may be a confusing factor for the diagnosis of Graves' ophthalmopathy. Recognition of the association between GD and thymic hyperplasia would avoid invasive diagnostic procedures and unnecessary surgical resection. Radioiodine therapy may be used in young children with repeated relapses of GD.

Thymic hyperplasia with lymphoepithelial sialadenitis (LESA)-like features: a case report and literature review.

BACKGROUND: Thymic hyperplasia with lymphoepithelial sialadenitis-like features (LESA-like TH) is a rare form of thymic hyperplasia, characterized by a prominent expansion of the thymic medulla containing hyperplastic lymphoid follicles with germinal centers, while an almost total absence of thymic cortex. Since the first report in 2012, only a few cases of LESA-like TH have been reported in the literature to date. Due to the rarity of LESA-like TH and the tumor-like morphology, it is easy to be misdiagnosed as other common diseases of the thymus in routine practice, such as thymoma and lymphoma. CASE PRESENTATION: Herein, we present a case report of a 52-year-old Chinese female patient with LESA-like TH, without any discomforting symptoms. Computer-tomography imaging revealed a cystic solid mass in the anterior mediastinum, with well-defined boundaries and multiple internal septa. Histologically, prominent features were florid lymphoid follicles containing germinal centers, as well as hyperplasia of thymic epithelial cells and proliferation of Hassall bodies. However, the thymic cortex rich in immature T cells was almost completely absent. Furthermore, mature plasma cells, lymphoepithelial lesions, and cholesterol clefts were frequently seen. CONCLUSION: We made a diagnosis of LESA-like TH and performed a literature review to better understand the clinicopathological features of LESA-like TH and reduce misdiagnosis.

Thymic Hyperplasia With Lymphoepithelial Sialadenitis-Like Features Arising in a Patient With Immunoglobulin G4-Related Disorders: A Case Report.

Thymic hyperplasia with lymphoepithelial sialadenitis-like features is characterized by thymic hyperplasia with lymphocytic infiltrates in the thymic epithelium. The lesion differs from other forms of thymic hyperplasia, including true and follicular thymic hyperplasia, in that it presents at an advanced age and has been reported to be unassociated with autoimmune diseases. We report a case of thymic hyperplasia with lymphoepithelial sialadenitis-like features in a 55-year-old male patient with a history of an immunoglobulin G4 (IgG4)-related disorder. Histologically, the resected mediastinal mass showed features consistent with those of thymic hyperplasia with lymphoepithelial sialadenitis-like features. In addition, the IgG4/IgG ratio was elevated in the polyclonal plasmacytoid infiltration. Thymic hyperplasia with lymphoepithelial sialadenitis-like features has not been reported to be associated with IgG4-related disorders; however, as shown in our report, it is crucial to include it in the differential diagnosis of a mediastinal mass in a patient with IgG4-related disorders.

MOG Antibody-Associated Disease and Thymic Hyperplasia: From the National Multiple Sclerosis Society Case Conference Proceedings.

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a recently described CNS inflammatory disorder that may manifest with optic neuritis, myelitis, seizures, and/or acute disseminated encephalomyelitis. While MOG-specific antibodies in patients with MOGAD are IgG1, a T-cell-dependent antibody isotype, immunologic mechanisms of this disease are not fully understood. Thymic hyperplasia can be associated with certain autoimmune diseases. In this report we describe a case of MOGAD associated with thymic hyperplasia in a young adult.

[Therapeutic approach to massive thymic hyperplasia associated with respiratory distress syndrome in a newborn infant living in a developing country: a case report]. / Stratégie thérapeutique devant une hyperplasie thymique massive associée à un syndrome de détresse respiratoire chez un nouveau-né dans un pays en voie de développement: à propos d'un cas.

Thymic hyperplasia is an anterior mediastinal mass with a variable clinical presentation. It causes differential diagnostic problems in the pediatric age group and there is no consensus on the therapeutic approach. We here report the case of a 1-month-old infant treated for respiratory distress syndrome. Chest CT scan revealed anterior mediastinal mass, which was excised through median sternotomy. Anatomopathological examination showed thymic hyperplasia. Clinical outcome was satisfactory. This encouraging result suggests that, contrary to what some authors propose, it would be more appropriate to opt for an aggressive therapeutic strategy when managing symptomatic thymic hyperplasia. This is even more justified in a socio-economic context characterised by difficult access to care and follow-up measures limited by patients' means.

[Thymic hyperplasia: A study of 46 cases]. / Les hyperplasies thymiques.

BACKGROUND: Thymic hyperplasia presents as an anterior mediastinal mass and poses important diagnostic and therapeutic challenge. Two types of thymic hyperplasia are described: true hyperplasia and follicular hyperplasie. Literature data are peculiar concerning both entities. We aimed to describe the clinical and microscopic characteristics of thymic hyperplasia through a single institution experience during an 11-year-period. METHODS: Thymic hyperplasia diagnosed during the period between 2009 and 2020 were included. RESULTS: In all, 46 thymic hyperplasias were diagnosed. The 46 patients consisted in 33 women and 13 men with a mean age of 30 years. Microscopic diagnosis concluded to a follicular hyperplasia in 12 cases and a true thymic hyperplasia in 34 cases. The diagnosis of true thymic hyperplasia posed a diagnostic challenge with an involuted thymus in 1 case and a thymolipoma in 1 case. The confrontation with the clinical data allowed retaining the diagnosis. CONCLUSION: The diagnosis of thymic hyperplasia is based on microscopic features. The confrontation with clinical data and the measurements of the thymus according to the age allow to retain the diagnosis in most challenging cases.

Massive true thymic hyperplasia in a 3-month-old infant: case report and literature review.

BACKGROUND: True thymic hyperplasia (TTH) is characterized as a distinct increase in both size and weight of thymus, which retains normal microscopic and immunohistochemical appearances. Massive true thymic hyperplasia (MTTH) is an extremely rare but significant subtype of TTH in pediatric ages due to its potentially serious consequences. It was reported that the age of cases with MTTH was predominantly between 1 and 15 years, while those before 1 year rarely occurred. By presenting the diagnosis and treatment process of our case as well as reviewing the related literature, we aimed to analyze the clinical characteristics of MTTH for patients younger than 1 year. CASE: A 3-month-old male infant was admitted to our department with a chief complaint of gradually increasing polypnea over 9 days, whose preoperative imaging examination showed a large intrathoracic soft tissue shadow predominantly on the right side. The percutaneous fine-needle biopsy guided by ultrasonography was performed to identify its diagnosis. However, proliferating lymphocytes and Hassall`s corpuscles were seen microscopically in the biopsy tissues, which were immunohistochemically positive for CD3, CD19, CD20, CD99, TdT, PCK and Ki67 ( > 90%). Due to the aggravating symptoms, a second operation with total thymectomy was carried out successfully for this infant, which confirmed the diagnosis of TTH again by both morphological study and immunohistochemical staining from the surgical specimen. CONCLUSIONS: By reviewing the literature, there were only 10 cases with MTTH reported between 1975 and 2020 for children aged < 1 year of life, together with our present one. In MTTH patient`s sex had an obviously male predominance (70%). Nine out of 10 presented initial symptoms or signs related to respiratory system and 6 patients showed respiratory distress. All patients were successfully treated by surgical thymectomy without any postoperative complications. The prognosis of MTTH was very successful.

Thymic rebound hyperplasia post-chemotherapy mistaken as disease progression in a patient with lymphoma involving mediastinum: a case report and reflection.

BACKGROUND: Chemotherapy can cause thymic atrophy and reduce T-cell output in cancer patients. However, the thymus in young adult patients has regenerative potential after chemotherapy, manifesting as thymic hyperplasia which can be easily mistaken as residual disease or recurrence in patients suffering lymphoma. CASE PRESENTATION: This study reports a case of lymphoma in a young female adult who was initially diagnosed with an anterior mediastinal mass, and was found to have soft tissue occupying the anterior mediastinum repeatedly after chemotherapy, suggesting a lymphoma residue or disease progression. From discussions by a multi-disciplinary team (MDT), the anterior mediastinal mass of the patient was considered unknown and might be thymus tissue or tumor tissue, and it was eventually identified as thymus tissue via histopathology. CONCLUSIONS: The anterior mediastinal mass appearing after chemotherapy in patients with lymphoma can be considered as enlarged thymus, and such phenomenon is frequent in young adult patients who undergo chemotherapy or autologous hematopoietic stem cell transplantation. Additionally, detection of thymic output cells in peripheral blood might be a feasible approach to differentiate thymic hyperplasia from lymphoma.

A rare association between true thymic hyperplasia and thyroid follicular tumor: a case report.

BACKGROUND: True thymic hyperplasia is a rare condition characterized by enlargement of the thymus while its normal structure is retained. True thymic hyperplasia is known to accompany Graves' disease, but no association between true thymic hyperplasia and thyroid follicular tumor has been reported so far. We report a case of true thymic hyperplasia in a patient with a thyroid follicular tumor. CASE PRESENTATION: A 52-year-old Japanese man was referred to our hospital for evaluation of a thyroid mass and a mediastinal mass. His serum thyroglobulin level was high, and hemithyroidectomy was performed to remove the thyroid mass. The resected mass was diagnosed as a follicular tumor of uncertain malignant potential. After resection of the thyroid lesion, the patient's serum thyroglobulin levels were markedly decreased. Seven months later, the patient underwent resection of the mediastinal mass. On pathological examination, the mass was found to consist of lobules, which formed a corticomedullary structure with Hassall's bodies, indicating a normal thymic mass with hyperplastic thymic tissue, less organized cellular cords, and intermingled adipose tissue. Immunostaining for cytokeratin 19 and cytokeratin 7 indicated that the lesion was consistent with thymic tissue. The lesion was diagnosed as true thymic hyperplasia, and the histological findings suggested that secondary atrophy had occurred. No evidence of recurrence was observed at 24 months after surgery. CONCLUSIONS: We present a case of a combination of true thymic hyperplasia and thyroidal follicular tumors that, to our knowledge, has not been reported previously. High serum thyroglobulin levels might play a role in hyperplasia of the thymus. Although true thymic hyperplasia is a rare disorder, it should be included in the differential diagnosis of a mediastinal mass in patients with thyroid disease.

Enfermedad de Graves-Basedow e hiperplasia tímica: una asociación que no nos debe extrañar / raves-Basedow disease and thymic hyperplasia: an association that must not surprise us

RESUMEN El aumento del tamaño del timo asociado a hiperplasia tímica (HT) es frecuente en los pacientes con enfermedad de Graves-Basedow (EGB), si bien es poco habitual detectarla en la práctica clínica diaria. Presentamos el caso de una mujer de 38 años con EGB, a quien se le detectó de manera incidental un aumento del timo. La paciente no tenía síntomas compresivos locales y la tomografía computarizada demostró engrosamiento homogéneo de mediastino anterior sugestivo de HT. Durante la evolución, se evidenció reducción del tamaño tras el control de la función tiroidea con fármacos antitiroideos. La presencia de algunas características radiológicas como aumento difuso y homogéneo de la glándula, ausencia de invasión de estructuras vecinas, calcificaciones o imágenes quísticas, sugiere la presencia de una HT. En estos casos, el tratamiento del hipertiroidismo y un control expectante son actitudes razonables. Conocer esta evolución puede evitar intervenciones diagnósticas o terapéuticas innecesarias.

ABSTRACT Thymic enlargement associated with thymic hyperplasia (TH), in patients with Graves-Basedow disease (GBD) is common, although it remains largely unrecognized in routine clinical practice. We present the case of a 38 year-old woman with GBD, to whom an incidental thymic enlargement was detected. The patient did not have local compressive symptoms and the computerized tomography showed homogenous thickening of the anterior mediastinum suggestive of TH. During evolution, a reduction in size was observed after thyroid function was controlled by anti-thyroid drugs. The presence of some radiological features such as diffuse and homogeneous gland enlargement, absence of invasion of neighboring structures, calcifications or cystic images suggests the presence of TH. In these cases treatment of hyperthyroidism and expectant management are reasonable responses. Recognizing this evolution can avoid unnecessary diagnostic or therapeutic interventions.

Rebound thymic hyperplasia after adrenalectomy in a patient with Cushing syndrome caused by adrenocortical adenoma: A case report.

RATIONALE: The development of rebound thymic hyperplasia (RTH) has been reported in patients who have recovered from stressful conditions such as surgery and steroid therapy. We report a case of RTH following the resolution of hypercortisolism after adrenalectomy for the treatment of adrenocortical adenoma in a patient with Cushing syndrome. PATIENT CONCERNS: A 5-month-old female infant with a history of overeating, hirsutism, and excessive weight gain for the previous 2 months was referred to the hospital. The laboratory results revealed elevated 24-hour urinary free cortisol levels. An overnight dexamethasone suppression test showed no response. Abdominal imaging revealed a right-sided suprarenal mass measuring 4_3cm. Histology showed an adrenocortical adenoma. Thus, she underwent a right adrenalectomy. DIAGNOSES: The patient showed clinical improvement with weight loss and normal cortisol levels over the next 4 months. Six months after the operation, a chest computed tomography showed enlargement of the left thymic lobe, which was previously nonexistent. INTERVENTIONS: A fine needle aspiration biopsy was performed, and histological examination revealed diffuse thymic hyperplasia. OUTCOMES: At the 1-year follow-up, the chest imaging studies showed resolution of the RTH. LESSIONS: An understanding of RTH after adrenalectomy as a treatment for cortisol-producing adrenocortical tumors is important for the prevention of unnecessary surgical intervention and therapy.

Thymic Hyperplasia Associated with Graves' Disease: Pathophysiology and Proposed Management Algorithm.

BACKGROUND: The association between Graves' disease (GD) and thymic hyperplasia (TH) was first described in 1912 and has been reported numerous times thereafter. TH associated with GD presents as an incidental mediastinal mass on chest X-ray or computed tomography (CT). The pathogenesis of TH in the setting of GD is unclear but seems to involve a complex interplay of hormonal and immunological mechanisms. SUMMARY: Here, the effect that thyroid hormones and autoimmunity have on thymic growth and size is reviewed. The authors' experience, along with a review of published case reports, reveals that general physicians may be unfamiliar with this association. This lack of familiarity may result in an aggressive management course, including surgical intervention, along with its associated risks and costs. The differential diagnosis and diagnostic workup of thymic enlargement associated with GD is discussed in light of the available clinical evidence. CONCLUSION: Recent literature confirms the generally benign nature of TH associated with GD, and supports a conservative approach for the diagnostic workup and initial management. Practical management recommendations for thymic enlargement associated with GD have been formulated and are presented here.

[True thymic hyperplasia : Differential diagnosis of thymic mass lesions in neonates and children]. / "Echte Thymushyperplasie" : Differenzialdiagnose der Thymusvergrößerung bei Säuglingen und Kindern.

Reactive and neoplastic thymic pathologies are the main considerations in the case of masses in the anterior and middle part of the mediastinum, while neurogenic tumors are predominant in the posterior mediastinum (which are not dealt with here). In neonates and infants, the commonest pathologies in the anterior mediastinum comprise germ cell tumors (mainly teratomas), congenital thymic cysts and true thymic hyperplasia (TTH). In toddlers, teratomas, yolk sac tumors and cysts predominate. In children over 5 years of age, lymphomas are the commonest mass lesions whereas thymomas and thymic carcinomas are rare. In addition, inflammation-linked hyperplasia in myasthenia gravis and rebound thymic hyperplasia after chemotherapy must be considered. Although rare at all ages, sarcomas must be considered in the differential diagnosis from birth onwards and throughout adolescence. Based on the report of a rare case of recurrent TTH, the differential diagnosis of this benign but potentially life-threatening condition is discussed.

Appearance of a thymic mass after treatment of Cushing's syndrome.

A 23-year-old woman was referred to our center with hirsutism, acne, weight gain, weakness, and irregular menses. Laboratory tests revealed increased levels of cortisol and sex hormones, and reduced adrenocorticotropic hormone levels. The patient underwent a right adrenalectomy. Pathology of the resected right adrenal gland showed an adrenal carcinoma. Computed tomography 8 months after the surgery revealed a thymic mass that was not detected preoperatively. The frequency of rebound thymic hyperplasia after normalization of hypercortisolism is not known, but possibly as high as 40%. Physicians must be aware of this phenomenon to avoid unnecessary thoracic surgery.

[Non-neoplastic lesions of the mediastinum]. / Nichtneoplastische Läsionen des Mediastinums.

The mediastinum is a complex body region of limited space but containing numerous organs of different embryonic origins. A variety of lesions that are difficult to distinguish from each other can occur here. Non-neoplastic lesions of the mediastinum represent important differential diagnostic pitfalls to mediastinal tumors, clinically, radiologically and histopathologically. It is important to bear these lesions in mind and to adequately verify or exclude them before starting further differential diagnostic considerations on mediastinal neoplasms. The most common non-neoplastic lesions in this region include cysts and lymphadenopathies. Mediastinal cysts result from abnormal events in the branching of the tracheobronchial tree, the pharyngeal pouches, the primary intestines, the pleuropericardial membranes and the brain meninges or are complications of inflammatory and hydrostatic processes. The histogenesis of the lining epithelium and the cyst wall structure are decisive for the exact classification. The histopathologically most prevalent patterns of mediastinal lymphadenopathies are those accompanied by increased histiocytes and Castleman's disease. Sclerosis is a non-specific reaction pattern of the mediastinum and can be associated with many processes; therefore, when establishing the diagnosis of sclerosing mediastinitis, several differential diagnoses have to be excluded. Simple thymic hyperplasia can be accompanied by considerable increase in organ size with severe local symptoms, while follicular thymic hyperplasia is often associated with myasthenia gravis and represents the most common findings in non-thymoma thymectomy specimens.

[VATS THYMECTOMY IN MYASTHENIA GRAVIS TREATMENT--A CASE REPORT]. / VATS TIMEKTOMIJA U LIJECENJU MIASTENIJE GRAVIS--PRIKAZ BOLESNICE.

Myasthenia gravis (MG) is a chronic autoimmune disease characterized by weakness of skeletal muscles, specifically ocular. Relationship between the thymus gland and MG is not fully understood yet. Thymectomy is recommended for individuals with thymoma, but should be considered in all patients under 60 years of age with generalized MG in cases with no thymomatous tissue. We report a 27-year-old female patient with ocular type myasthenia gravis and radiological findings of anterior mediastinal mass, treated by VATS thymectomy. The intervention was carried out by 3-portal right-sided thoracoscopic approach. Single-lung ventilation and carbon-dioxide insufflation provided working space, and harmonic scalpel was used for the dissection and ligation. The patient's postoperative course was uncomplicated and the patient was discharged on the third postoperative day. The aim of our case report is to stress the importance of VATS technique in faster recovery and better cosmetic effect than in sternotomy procedures.

MuSK autoantibodies in myasthenia gravis detected by cell based assay--A multinational study.

Seronegative myasthenia gravis (MG) presents a serious gap in MG diagnosis and understanding. We applied a cell based assay (CBA) for the detection of muscle specific kinase (MuSK) antibodies undetectable by radioimmunoassay. We tested 633 triple-seronegative MG patients' sera from 13 countries, detecting 13% as positive. MuSK antibodies were found, at significantly lower frequencies, in 1.9% of healthy controls and 5.1% of other neuroimmune disease patients, including multiple sclerosis and neuromyelitis optica. The clinical data of the newly diagnosed MuSK-MG patients are presented. 27% of ocular seronegative patients were MuSK antibody positive. Moreover, 23% had thymic hyperplasia suggesting that thymic abnormalities are more common than believed.