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True thymic hyperplasia results from stressful situations such as chemotherapy. It commonly presents as an anterior mediastinal mass; cervical location is exceptional. Here we report a case of a cervical true thymic hyperplasia in a 12-year-old girl who had a Hodgkin lymphoma treated by radiotherapy and chemotherapy. She was referred to our department for a left cervical mass. The PET scan showed a hypermetabolic adenopathy. Mediastinal MRI was unremarkable. The patient underwent resection of the cervical mass under general anesthesia. Pathological examination confirmed the diagnosis of a true thymic hyperplasia. The aim of this paper is to illustrate a case of an incidental ectopic cervical thymic hyperplasia in a patient treated for Hodgkin lymphoma., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Rebound thymic hyperplasia (RTH) is a common phenomenon caused by stress factors such as chemotherapy (CTX) or radiotherapy, with an incidence between 44% and 67.7% in pediatric lymphoma. Misinterpretation of RTH and thymic lymphoma relapse (LR) may lead to unnecessary diagnostic procedures including invasive biopsies or treatment intensification. The aim of this study was to identify parameters that differentiate between RTH and thymic LR in the anterior mediastinum., Methods: After completion of CTX, we analyzed computed tomographies (CTs) and magnetic resonance images (MRIs) of 291 patients with classical Hodgkin lymphoma (CHL) and adequate imaging available from the European Network for Pediatric Hodgkin lymphoma C1 trial. In all patients with biopsy-proven LR, an additional fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT was assessed. Structure and morphologic configuration in addition to calcifications and presence of multiple masses in the thymic region and signs of extrathymic LR were evaluated., Results: After CTX, a significant volume increase of new or growing masses in the thymic space occurred in 133 of 291 patients. Without biopsy, only 98 patients could be identified as RTH or LR. No single finding related to thymic regrowth allowed differentiation between RTH and LR. However, the vast majority of cases with thymic LR presented with additional increasing tumor masses (33/34). All RTH patients (64/64) presented with isolated thymic growth., Conclusion: Isolated thymic LR is very uncommon. CHL relapse should be suspected when increasing tumor masses are present in distant sites outside of the thymic area. Conversely, if regrowth of lymphoma in other sites can be excluded, isolated thymic mass after CTX likely represents RTH., (© 2023 The Authors. Pediatric Blood & Cancer published by Wiley Periodicals LLC.)

We treated a 22-year-old woman suffering from Graves' disease and thymic hyperplasia. She was referred to our institution for a close investigation of thyrotoxicosis and thymic mass. Thyroid tests and magnetic resonance imaging resulted in a diagnosis of Graves' disease and thymic hyperplasia. The thyroid function and thyroid-stimulating hormone receptor antibody (TRAb) were normalized one and five months after thiamazole initiation, respectively. The thymic size began to decrease after 1 month and was further decreased after 5 months; it was normalized after 12 months. The correlation between TRAb titers and the thymic size (R 2 =0.99) suggested that the patient's autoimmunity might have contributed to the thymic hyperplasia.

Background: Detection of fat content in thymic lesions is crucial to differentiate thymic hyperplasia from thymic tumors or other anterior mediastinal pathologies., Purpose: To assess the feasibility of dual-energy CT (DECT) fat content quantification for the differentiation of anterior mediastinal lesions from benign thymic lesions and the normal spectrum of the thymus., Materials and Methods: Chest DECT images of 465 patients (median 61 years, 63% female) were visually evaluated by two radiologists and semiquantitatively scored based on the degree of fatty degeneration ranging from completely fatty (score 0) to predominantly soft-tissue (score 3), and anterior mediastinal mass (score 4). A subset of scans (n =134 including all cases with scores 2-4 and 20 randomly-selected cases from scores 0 and 1) underwent quantitative DECT analysis (fat fraction, iodine density, and conventional CT value). DECT values were compared across the semiquantitative scores., Results: Results of visual evaluation included 35 with predominantly solid thymus (score 3) and 15 with anterior mediastinal mass (score 4). The most common clinical diagnoses of the 15 masses (including 8 with pathologic confirmation) were metastases (n = 10) and lymphoma (n = 4). CT values in the abnormal thymus were significantly higher than those in score 3 (median: 69.7 HU versus 19.9 HU, P <0.001). There was no significant difference in iodine density values (median: 1.7 mg/ml versus 1 mg/ml, P = 0.09). However, the fat fraction value was significantly lower in the abnormal thymus (score 4) than in the predominantly soft-tissue attenuation thymuses (score 3) (median: 12.8% versus 38.7%, P <0.001). ROC curve analysis showed that fat fraction had an AUC of 0.96 (P <0.001), with a cutoff of <39.2% fat fraction yielding 100% sensitivity and 85% specificity., Conclusion: DECT fat fraction measurements of the thymus may provide additional value in distinguishing anterior mediastinal lesions from benign thymus. Use of DECT may reduce the need for subsequent imaging evaluation., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Pure red cell aplasia caused by true thymic hyperplasia is extremely rare. We report the case of a 25-year-old female diagnosed with pure red cell aplasia. Following a thymectomy confirming true thymic hyperplasia and corticosteroid therapy, complete response was achieved. Patients diagnosed with pure red cell aplasia should be investigated with a computerized tomographic scan to assess for thymic pathology and if present, this should be resected. Follow-up is essential to monitor for recurrence., (© The Author(s) 2021. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery.)

Introduction: True thymic hyperplasia following chemotherapy has been described mostly in children. There are a few cases of thymus hyperplasia that have been reported in breast cancer patients. Diagnosis of this unusual entity is very crucial to pretend unnecessary surgery or interventional diagnostic procedures., Case Presentation: We report a case of thymus hyperplasia in a patient who was operated and treated with adjuvant chemotherapy for stage 2 breast cancer two years ago. In the follow-up CT scans, an anterior mediastinal mass was noted. Radiologic evaluation and follow-up revealed thymus enlargement., Discussion: Thymic hyperplasia following chemotherapy has been described in both children and adults, but occurs mostly in children and adolescents treated for lymphoma and several other types of tumors. Few cases are reported in literature describing thymus hyperplasia following chemotherapy in a breast cancer patient. The imaging findings of thymic hyperplasia on CT, MRI and PET CT are discussed., Conclusion: Radiologists must be aware of this unusual finding in breast cancer patients treated with chemotherapy to guide the clinicians appropriately in order to avoid unnecessary surgical intervention, additional invasive diagnostic procedures, or chemotherapy., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Objectives: To evaluate the effectiveness of CT texture analysis (CTTA) in (1) differentiating Thymoma (THY) from thymic hyperplasia (TH) (2) low from high WHO grade, and (3) low from high Masaoka Koga (MK)/International Thymic Malignancy Interest Group (ITMIG) stages., Methods: After institute ethical clearance, this cross-sectional study analyzed 26 patients (THY-18, TH-8) who underwent dual energy CT (DECT) and surgery between January 2016 and December 2018. CTTA was performed using TexRad (Feedback Medical Ltd., Cambridge, UK- www.fbkmed.com) by a single observer. Free hand regions of interest (ROIs) were placed over axial sections where there was maximum enhancement and homogeneity. Filtration histogram was used to generate six first-order texture parameters [mean, standard deviation (SD), mean of positive pixels (MPP), entropy, skewness, and kurtosis] at six spatial scaling factors "SSF 0, 2, 3, 4, 5, and 6". Mann-Whitney test was applied among various categories and p value < 0.05 was considered significant. Three-step feature selection was performed to determine the best parameters among each category., Results: The best performing parameters were (1) THY vs TH- Mean at "SSF 0" (AUC: 0.8889) and MPP at "SSF 0" (AUC: 0.8889), (2) Low vs high WHO grade - no parameter showed statistical significance with good AUC, and (3) Low vs high MK/ITMIG stage- SD at "SSF 6" (AUC: 0.8052 and 0.8333 respectively])., Conclusion: CTTA revealed several parameters with excellent diagnostic performance in differentiating thymoma from thymic hyperplasia and MK/ITMIG high vs low stages. CTTA could potentially serve as a non-invasive tool for this stratification., Advances in Knowledge: This study has employed texture analysis, a novel radiomics method on DECT scans to determine the best performing parameter and their corresponding cut-off values to differentiate among the above-mentioned categories. These new parameters may help add another layer of confidence to non-invasively stratify and prognosticate patients accurately which was only previously possible with a biopsy.

Competing Interests: Disclosure The authors report no conflicts of interest in this work.

The thymus is a primary lymphoid organ that plays a key role in the immune system development. Normally, it is located in the anterior mediastinum and it changes tissue composition with progressive fatty involution with age. The spectrum of pathological processes involving the thymus include enlargement, tumour development, and cystic change. In addition, other local pathology can mimic thymic disease. Differentiating these entities can be challenging; however, recognizing key features on imaging is essential to appropriately guide further investigation and therapy. The focus of this pictorial review will be to highlight the important distinguishing features of thymic hyperplasia, thymomas, thymic cysts, thymic neuroendocrine tumours (NETs), thymolipomas, mediastinal teratomas, and other mimics of thymic disease. Knowledge of the varying imaging findings on computed tomography and magnetic resonance imaging is valuable for radiologists to appropriately classify disease, avoid misdiagnosis, and expedite therapy., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The appearance of the paediatric thymus changes as the normal process of thymic involution occurs. Thymic tissue may be orthotopic within the anterior mediastinum or ectopically located along the course of its embryological development. The variable appearance of orthotopic and ectopic thymic tissue in children on imaging studies may lead to misinterpretation of the normal thymus as pathology. Recognition of normal thymic tissue can mitigate unnecessary further diagnostic testing and patient anxiety. In this review, we discuss the embryological development and anatomical variants of normal thymus, and demonstrate the multimodality imaging features of the normal thymus in children, including positron-emission tomography, and diffusion-weighted imaging and in- and opposed-phase imaging on magnetic resonance imaging. We demonstrate the normal thymus mimicking pathological processes and discuss features that distinguish normal thymus, including thymic rebound hyperplasia, from pathology., (Copyright © 2021 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Anterior mediastinum is the most common location of mediastinal tumors, which include various solid and cystic lesions. The lesion location and CT and MRI features are important in the differential diagnosis. Recently, CT-based mediastinal compartment classification systems were proposed and suggested to be useful for accurate evaluation of mediastinal lesions. CT and MRI reflect the pathological findings of mediastinal lesions, and knowledge of the pathological features is important for the differential diagnosis. In this article, we review the CT and MRI features of anterior mediastinal lesions and describe important points in the differential diagnosis.

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.

Background: Patients with COVID-19 (COVID) may develop acute respiratory distress syndrome with or without sepsis, coagulopathy and visceral damage. While chest CT scans are routinely performed in the initial assessment of patients with severe pulmonary forms, thymus involvement and reactivation have not been investigated so far., Methods: In this observational study, we systematically scored the enlargement of the thymus and the lung involvement, using CT scans, in all adult patients admitted to the ICU for COVID or any other cause (control group) at one centre between March and April 2020. Initial biological investigations included nasal detection of SARS-CoV-2 ribonucleic acid by polymerase chain reaction (PCR). In a subgroup of 24 patients with different degrees of pulmonary involvement and thymus hypertrophy, plasma cytokine concentrations were measured and the export of mature T cells from the thymus was estimated simultaneously by PCR quantification of T cell receptor excision circles (TRECs)., Results: Eighty-seven patients were studied: 50 COVID patients and 37 controls. Non-atrophic or enlarged thymus was more commonly observed in COVID patients than in controls (66% vs. 24%, p < 0.0001). Thymus enlargement in COVID patients was associated with more extensive lung injury score on CT scans (4 [3-5] vs. 2 [1.5-4], p = 0.01), but a lower mortality rate (8.6% vs. 41.2%, p < 0.001). Other factors associated with mortality were age, lymphopaenia, high CRP and co-morbidities. COVID patients had higher concentrations of IL-7 (6.00 [3.72-9.25] vs. 2.17 [1.76-4.4] pg/mL; p = 0.04) and higher thymic production of new lymphocytes (sj/βTREC ratio = 2.88 [1.98-4.51] vs. 0.23 [0.15-0.60]; p = 0.004). Thymic production was also correlated with the CT scan thymic score (r = 0.38, p = 0.03) and inversely correlated with the number of lymphocytes (r = 0.56, p = 0.007)., Conclusion: In COVID patients, thymus enlargement was frequent and associated with increased T lymphocyte production, which appears to be a beneficial adaptation to virus-induced lymphopaenia. The lack of thymic activity/reactivation in older SARS-CoV-2 infected patients could contribute to a worse prognosis.

Magnetic resonance imaging (MRI) has become a crucial tool for evaluating mediastinal masses considering that several lesions that appear indeterminate on computed tomography and radiography can be differentiated on MRI. Using a three-compartment model to localize the mass and employing a basic knowledge of MRI, radiologists can easily diagnose mediastinal masses. Here, we review the use of MRI in evaluating mediastinal masses and present the images of various mediastinal masses categorized using the International Thymic Malignancy Interest Group's three-compartment classification system. These masses include thymic hyperplasia, thymic cyst, pericardial cyst, thymoma, mediastinal hemangioma, lymphoma, mature teratoma, bronchogenic cyst, esophageal duplication cyst, mediastinal thyroid carcinoma originating from ectopic thyroid tissue, mediastinal liposarcoma, mediastinal pancreatic pseudocyst, neurogenic tumor, meningocele, and plasmacytoma., Competing Interests: The authors have no potential conflicts of interest to disclose., (Copyright © 2021 The Korean Society of Radiology.)

A 6-mo-old female Beagle dog was inappetent and depressed. The radiographic, ultrasonographic, and computed tomographic examination of the chest revealed a 10 × 7 cm multicystic mediastinal structure interpreted as altered thymus, in association with moderate pleural effusion that laboratory tests confirmed as hemothorax. No history of trauma or anticoagulant drug intoxication was reported, and no coagulation disorders were detected. Afterward, medial cranial sternotomy was performed to remove the altered tissue. Histologically, this tissue was compatible with a thymic remnant, characterized by numerous cystic lesions, mostly blood filled and lined by flattened-to-cuboidal epithelial cells, occasionally projecting into the surrounding stroma, and forming cytokeratin-positive ribbons, trabeculae, and papillae. Lymphocytes were scant, and numerous areas of congestion and hemorrhage were present throughout the samples. This case of idiopathic thymic hemorrhage with cystic degeneration of the thymus and pseudoepitheliomatous hyperplasia was an incidental finding; the dog recovered from surgery uneventfully.

Introduction: Thymic regrowth after chemotherapy treatment has been reported in children with lymphoma, and in order to avoid misdiagnosing these cases as relapses, physicians should become familiar with rebound (reactive) thymic hyperplasia (RTH) and remain aware of its possible occurrence. We aimed to estimate the prevalence of RTH in children with lymphoma after completion of chemotherapy and to evaluate the clinical characteristics, outcomes, and the findings of computed tomography (CT) and gallium-67 (GA-67) scans in these patients., Patients and Methods: We conducted a retrospective cross-sectional study by reviewing the health records of children with a lymphoma diagnosis managed at an outpatient paediatric oncology clinic in Jeddah, Saudi Arabia., Results: Rebound thymic hyperplasia was detected in 51.9% of the lymphoma patients (14/27). It developed a median of 2.5 months after completion of chemotherapy (range, 2.0-4.25 months). Patients with RTH had significantly shorter treatment durations, and we found no significant differences between patients with and without RTH in sex, age at diagnosis, type of lymphoma or type of treatment received. All patients with RTH were asymptomatic, and routine laboratory tests did not detect any abnormalities in them. The findings of CT and GA-67 scans were highly suggestive of RTH. None of the patients with RTH had a recurrence, and RTH resolved spontaneously within a median of 6 months (range, 4.0-11.0)., Conclusion: RTH was detected in ∼50% of children with lymphoma after completion of chemotherapy. A clinical evaluation and laboratory tests combined with imaging by CT and GA-67 can help identify RTH and rule out other lesions elsewhere., (Copyright © 2019 Asociación Española de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.)

Background: Malignant ovarian germ cell tumours typically require multimodal therapy including surgery and systemic platinum-based chemotherapy. Most patients are cured, with survival rates exceeding 95%., Case: This report describes an unusual case of ovarian germ cell tumour (GCT) recurring 15 years after surgery and manifesting as metastatic disease to the liver, lung, and retroperitoneal lymph nodes., Conclusion: Thymic hyperplasia was a confounding finding in this case, and it should be considered in the differential diagnosis of a mediastinal mass in heavily treated patients with GCT., (Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.)

The familial occurrence of thymic pathology, even though rare, is widely reported in the literature and mainly concerns cases of familial autoimmune myasthenia gravis. Other less frequent cases of familial occurrence of thymoma, thymic carcinoid and thymic hyperplasia have been described. It seems that the familial occurrence is poorly recorded and thus its prevalence is underestimated. We report two families whose members presented different forms of thymic pathology and discuss the necessity of screening programs in family members of patients presenting a thymic lesion.

Background: Thyrotoxicosis and orbitopathy are the best-known expressions of Graves' disease. There are also rarer and less-known phenomena, such as thymic hyperplasia. Identification of these is important in order to avoid potentially unnecessary invasive interventions., Case Description: In the case of two young women with lung embolisms, CT pulmonary angiography also revealed an enlarged thymus. This turned out to be caused by as of yet unknown Graves' disease. Since pathological examination of a thymus-biopsy sample was unable to rule out thymoma, thymectomy was performed on the first patient. Pathological examination of the entire thymus revealed hyperplasia. Additional FDG-PET/CT scan of the second patient revealed diffuse hyperactivity in the diffusely enlarged thymus. In this case, we opted for expectant treatment. A follow-up FDG-PET/CT scan 1 year later, revealed a non-abnormal thymus., Conclusion: An enlarged thymus caused by thymic hyperplasia is a less well-known manifestation of Graves' disease. In case additional abnormalities develop in patients with Graves' disease, it is important to consider that these might be related to the disease before diagnosing an additional new condition.

Purpose: To compare the post-thymectomy prognosis in different conditions of myasthenia gravis (MG) patients with thymus hyperplasia., Materials and Methods: Collecting medical record and carrying out the follow-up study of 123 myasthenia gravis patients with thymus hyperplasia who have underwent thymectomy during the period between 2003 and 2013. Dividing into different groups based on gender, age of onset, duration of disease and Myasthenia Gravis Association of America (MGFA) clinical classification to analyze different prognosis in different groups., Results: Complete stable remission (CSR) was achieved in 71 of 123 patients (59.5%). There is no gender-related difference in achieving CSR. Patients with early onset of MG (≤40 years old) or disease duration less than 12 months had significantly higher CSR rates than those with late onset of MG (>40 years old) or disease duration more than 12 months respectively, while no difference was found in remission rate between MGFA clinical classification I and MGFA II., Conclusion: Myasthenia gravis patients with thymus hyperplasia who had thymectomy are proved to possess greater chance of achieving CSR. The onset age of disease and duration are the prognostic factors.

Background: Development of mediastinal masses after completion of chemotherapy in pediatric patients with malignant lymphoma is worrisome and challenging to clinicians., Methods: We performed a retrospective review of 67 patients with lymphoma treated at our hospital from January 1, 2001 to June 1, 2013. Patients who received at least two chest computed tomography (CT) examinations after complete remission (CR) was achieved were further analyzed. Gallium-67 scans and positron emission tomography (PET) were recorded and compared between these patients., Results: Sixty-two of 67 patients reached CR, of whom 31 (22 male, 9 female) were patients that received at least two chest CT examinations after CR. Rebound thymic hyperplasia (RTH) was diagnosed in 21/31 patients (67.7%), including 14/23 (60.9%) and seven out of eight (87.5%) with non-Hodgkin's lymphoma and Hodgkin's lymphoma, respectively. Ages ranged from 3 years to 18 years (median 10 years). Increased radioactivity uptake of the anterior mediastinum in gallium scans was found in nine out of 20 patients (45%) with thymic rebound. PET was performed in six out of 21 patients. Increased fluorodeoxyglucose (FDG)-avid uptake in the anterior mediastinum was observed in four of six patients (66.7%) by PET. One patient received thymectomy. No patients with RTH had lymphoma relapse within the median follow-up period (5 years). Relapse was statistically significantly different (p = 0.001) between patients with and without RTH., Conclusion: RTH developed in 67.7% of pediatric patients with lymphoma in CR after chemotherapy. The association of RTH development and lowered relapse rates has yet to be determined. Awareness of this phenomenon is important in the prevention of unnecessary surgical intervention or chemotherapy., (Copyright © 2016. Published by Elsevier B.V.)

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.

Thymic hyperplasia is frequently observed in Graves' disease. However, detectable massive enlargement of the thymus is rare, and the mechanism of its formation has remained elusive. This case showed dynamic changes in thymic hyperplasia on serial computed tomography images consistent with changes in serum thyrotropin receptor (TSH-R) antibodies and thyroid hormone levels. Furthermore, the patient's thymic tissues underwent immunohistochemical staining for TSH-R, which demonstrated the presence of thymic TSH-R. The correlation between serum TSH-R antibody levels and thymic hyperplasia sizes and the presence of TSH-R in her thymus suggest that TSH-R antibodies could have a pathogenic role in thymic hyperplasia.

Objectives: The purposes of this study were to assess the feasibility of fetal thymus measurement between 13 and 16 weeks' gestation, to evaluate the potential difference using color Doppler sonography with the thy-box technique, and to construct normal percentile ranges., Methods: This retrospective study included 287 healthy singleton pregnancies. The fetal thymus was shown in an axial plane of the upper mediastinum. Color Doppler imaging was applied to outline the thy-box: ie, the area between the brachiocephalic artery posteriorly and internal mammary arteries laterally. Measurements of the lateral and anteroposterior diameters of the thymus with and without color Doppler imaging were compared., Results: The thymus was shown in 95% of the cases (273 of 287) between 13 and 16 weeks' gestation. The mean lateral thymus diameter ± SD with color Doppler imaging (5.30 ± 0.7 mm) was significantly longer in comparison to the measurement without color Doppler imaging (5.06 ± 0.8 mm; P < .001), whereas the anteroposterior diameter was significantly shorter (3.19 ± 0.9 versus 3.26 ± 0.8 mm; P = .044). Normal percentiles of thymus measurements for gestational age were constructed., Conclusions: The fetal thymus can be clearly and accurately shown as early as 13 weeks' gestation by using the thy-box. Measurements with color Doppler imaging were significantly different from those without and hence are preferable, as color Doppler imaging can delineate the thymus borders more accurately., (© 2015 by the American Institute of Ultrasound in Medicine.)

Objectives: To analyse the clinical and computed tomography (CT) findings related to reactive thymic hyperplasia in order to improve the recognition of this phenomenon and avert over-treatment., Methods: Fifty-two children with pathologically proven lymphoma developed reactive thymic hyperplasia following chemotherapy, which was confirmed with long-term review and follow-up. The clinical and CT findings of these 52 children were retrospectively analysed., Results: The median follow-up period for the whole study group was 32.9 months. Fifty-one children survived free of disease; 23 of these had been with tumour invasion and the remaining 29 without. The median period from complete remission (CR) of the mediastinal lesions to the date of recurrent mediastinal masses was 8.6 months, which was not statistically significantly different from that of 9.5 months from commencement of treatment to the date of newly developed mediastinal masses (P = 0.495). The median maximal diameters of the recurrent and newly developed mediastinal masses were not significantly different (P = 0.091). All of the 52 cases presented with a single mediastinal mass; 42 masses (42/52, 81%) of those showed trapezoidal or triangular shapes and were well-circumscribed; 10 masses (10/52, 19%) manifested diffuse shapes and were ill-circumscribed. Forty-two masses (42/52, 81%) showed homogeneous density. All of the masses revealed mild enhancement after contrast administration. Forty-two masses (42/52, 81%) slightly displaced and 10 masses (10/52, 19%) partly surrounded adjacent vessels. After long-term follow-up, 42 masses (42/52, 81%) shrank naturally, and 10 (10/52, 19%) remained unchanged., Conclusions: Reactive thymic hyperplasia can, and often does, occur in children receiving regular chemotherapy for lymphoma, regardless of whether the tumour initially invades the mediastinum. Knowing the characteristic CT findings of this benign entity is helpful in differentiating it from residual or recurrent lymphoma and averting unnecessary treatment., (© The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Purpose: To determine the non-therapeutic thymectomy rate in a recent six-year consecutive thymectomy cohort, the etiology of these unnecessary thymectomies, and the differentiating CT features of thymoma, lymphoma, thymic hyperplasia, and thymic cysts., Materials and Methods: Electronic data base query of all thymectomies performed at the Massachusetts General Hospital from 2006 to 2012 yielded 160 thymectomy cases, 124 of which had available imaging. The non-therapeutic thymectomy rate (includes thymectomy for lymphoma and benign disease) was calculated. Preoperative clinical and CT imaging features were assessed by review of the in-house electronic medical record by 2 thoracic surgeons and 2 pathology-blinded radiologists, respectively., Results: The non-therapeutic thymectomy rate of 43.8% (70/160) was largely secondary to concern for thymoma and was comprised of lymphoma (54.3%, 38/70), thymic bed cysts (24.3%, 17/70), thymic hyperplasia (17.1%, 12/70), and reactive or atrophic tissue (4.3%, 3/70). Among these four lesions, there were significant differences in location with respect to midline, morphology, circumscription, homogeneity of attenuation, fatty intercalation, coexistent lymphadenopathy, overt pericardial invasion, and mass effect (p<0.001). True thymic cysts ranged in attenuation from -20 to 58Hounsfield units (HU), with a mean attenuation of 23HU., Conclusion: The high rate of unnecessary thymectomy was due to misinterpretation of thymic cysts, thymic hyperplasia, and lymphoma as thymoma on chest CT. This study demonstrates differentiating features between thymoma, lymphoma, thymic hyperplasia, and thymic cysts on chest CT which may help triage more patients away from thymectomy toward less invasive and non-invasive means of diagnosis and thereby lower the non-therapeutic thymectomy rate., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

The thymus is routinely encountered on cross-sectional imaging studies of the chest. It has a variable appearance, undergoes dynamic changes during periods of stress, and demonstrates numerous different pathologic lesions. Understanding the imaging characteristics of these different lesions facilitates accurate radiographic diagnosis and can prevent unnecessary follow-up imaging and intervention. This article will review normal thymic anatomy and development, thymic hyperplasia and associated medical conditions, and the imaging and pathologic features of various benign and malignant thymic lesions., (Copyright © 2015 Canadian Association of Radiologists. Published by Elsevier Inc. All rights reserved.)

Purpose: To report five cases of patients diagnosed with differentiated thyroid carcinoma (DTC) with uptake in the thymic area after high-dose treatment with I-131 and to evaluate the potential causes and therapeutic management., Methods: Five cases of young female patients with a mean age of 36.6 years (24-43) who had been treated with a mean dose of 106 mCi of I-131 (100-150 mCi) showing tracer uptake in the thymic area are reported. An I-131 whole-body scan (131I-WBS) was performed 7 days after therapeutic dose administration to each patient. Anterior and posterior planar images, followed by SPECT/CT of the head, neck and superior mediastinum were acquired in all patients. Thyroglobulin levels were measured with and without hormone replacement therapy in all cases. Samples taken from the superior mediastinum were sent to pathology for analysis, which confirmed the presence of thymic tissue., Results: Two patients underwent elective total thymectomy due to the gross characteristics of the gland, local 131-I uptake, and high thyroglobulin levels. The remaining three patients had already undergone thymectomy as part of neck dissection during initial surgery, and no further invasive interventions were therefore performed. Pathological examination revealed no metastases in these five patients., Conclusions: Thymus visualization in young patients after administration of therapeutic doses of I-131 seems to be a more common finding than usually thought. Absence of metastasis in the thymus despite high thyroglobulin levels was confirmed in all cases. Based on these results, we suggest that a more expectant and less aggressive therapeutic approach could be used. We also suggest that I-131 therapy for DTC should be considered in classification of the potential causes of true thymic hyperplasia in the subgroup of patients recovering from a stressor., (Copyright © 2013 SEEN. Published by Elsevier Espana. All rights reserved.)

Background: Rebound thymic hyperplasia (RTHP) is not an uncommon finding after radiation or chemotherapy in patients with various malignancies. However, there are limited case reports of this phenomenon after radioactive iodine ablation therapy (RIAT) in differentiated thyroid cancer (DTC). The goal of this study was to evaluate the incidence, patterns, and factors affecting RTHP after RIAT using (18)F-FDG PET/CT., Methods: The study design was a retrospective review of 2550 patients (568 men, 1982 women; age 13-79 years) who underwent FDG PET/CT imaging after total thyroidectomy and RIAT from June 2009 through June 2012. Patients were divided into four age-related subgroups. Overall incidence, age-related incidences, and sex distribution were evaluated in patients with thymic FDG uptake on PET/CT (RTHP+). The correlation between incidence of RTHP and age was assessed using the Cochran-Armitage trend test. The Wilcoxon rank-sum test and multiple regression were applied to investigate the effect of applied dose of radioactive iodine (RAI) and age on the incidence of RTHP. Correlations of standardized uptake value (SUV) and thymic volume with age and morphologic type were also evaluated., Results: Overall incidence of RTHP after RIAT was 1.49%, and all of the RTHP+ patients except one were female. The Cochran-Armitage trend test revealed significantly decreased incidence from the second to fifth decade (8.84%, 1.74%, 0.98%, and 0.39% respectively; p<0.001). In each age-related subgroup, the RAI dose was significantly higher in the RTHP+ than RTHP- group (p<0.001), while there was no difference in RAI dose in RTHP+ patients among age-related subgroups (p=0.838). SUVmean and SUVmax of RTHP revealed no meaningful correlation with RAI dose or age. There were no differences among morphologic patterns of RTHP in age distribution and ablation dose., Conclusions: RTHP after RIAT showed a strong female predominance, despite the higher administration dose of RAI in male patients. Although the decreased incidence of RTHP after RIAT with age is similar to the pattern of RTHP induced by other causes, the fact that older patients, even sixth decade patients, can present with RTHP after RIAT is noteworthy in the management of DTC.

Rationale and Objectives: To determine the intraobserver and interobserver variabilities of thymic measurements on computed tomography (CT) in patients with pathologic diagnosis of thymic hyperplasia or normal thymus., Materials and Methods: Thirty-three patients with pathologic diagnosis of thymic hyperplasia (n = 25) or normal thymus (n = 8) who had identifiable thymus gland on CT were retrospectively studied. Two radiologists independently measured thymic size and CT attenuation. Concordance correlation coefficients (CCCs) and Bland-Altman plots were used to assess intraobserver and interobserver agreements., Results: The intraobserver and interobserver agreements of thymic diameters and the lobe length were moderate, with CCCs ranging from 0.73 to 0.89 and from 0.72 to 0.81, respectively. Higher agreement was noted among patients whose measurements were performed on the same CT image in two independent measurements, with intraobserver CCC ≥ 0.95 for diameters and length. After providing readers with an instruction for consistent selection of CT image for measurements, the intraobserver and interobserver agreements improved, resulting in CCCs ranging from 0.81 to 0.92 and from 0.77 to 0.85 for diameters and length, respectively. Thymic lobe thickness had the least agreement. CT attenuation measurements were highly reproducible, with CCCs ranging from 0.88 to 0.97. In patients with thymic CT attenuation >30 HU (Hounsfield unit), the attenuation measurements were more reproducible with narrower 95% limits of agreement., Conclusions: Thymic size measurements had moderate-to-high intraobserver and interobserver agreements, when the instruction for consistent selection of images was provided to the readers. CT attenuation was highly reproducible, with higher reproducibility for thymic glands with >30 HU. Awareness of thymic measurement variability is necessary when interpreting measured values of normal thymus and thymic pathology on CT., (Copyright © 2014 AUR. Published by Elsevier Inc. All rights reserved.)

Objective: Thymus alterations have been related to several autoimmune disorders. In particular, previous studies identified a significant frequency of gland abnormalities by chest high-resolution CT (HRCT) in SSc patients. In this study we aimed to investigate the prevalence of radiological thymic alterations and their correlation with clinical and serological features in a large SSc series., Methods: We retrospectively evaluated thymic shape on CT scans of 200 consecutive, unselected SSc patients aged over 30 years The presence of radiological abnormalities, i.e. enlarged gland >13 mm or nodular lesions >7 mm, was correlated with SSc clinico-serological features. Moreover, the patients were also classified using a second thickness cut-off of 7 mm in order to identify incomplete thymic involution., Results: Twenty-four of 200 (12%) SSc patients presented an abnormal thymus at HRCT, including hyperplasic (19/24) and nodular (5/24) glands. Otherwise, using the cut-off of 7 mm for gland thickness and excluding subjects with nodular thymus, 50/195 (25.6%) patients presented an incomplete thymic involution. Thymic radiological alterations are significantly correlated with younger age and diffuse cutaneous SSc. Moreover, an abnormally enlarged thymus tended to be more common in patients with shorter disease duration., Conclusion: The present report on a large series of SSc patients further reinforces previous data present in the literature that includes other cohort studies and a number of anecdotal observations. Even though the actual role of thymus radiological abnormalities remains unclear, possible involvement of the gland in the early phase of immune-mediated SSc pathogenesis might be supposed.

Background: Thymectomy is often performed on the basis of computed tomography scan findings that are suspicious for thymoma. However, the final diagnosis may be a condition such as thymic hyperplasia or lymphoma for which thymectomy is not therapeutic. The present analysis was undertaken to determine the prevalence of a "nontherapeutic" thymectomy., Methods: The Nationwide Inpatient Sample from 2000 through 2009 was queried to identify patients who underwent a thymectomy. Only adult patients who underwent a total thymectomy without other associated procedures were analyzed. Patients with a diagnosis of myasthenia were excluded. A nontherapeutic thymectomy was defined as a patient who underwent thymectomy with an International Classification of Diseases, Ninth Revision diagnosis code of lymphoma, thymic hyperplasia, thymic cyst, or other benign diseases of the thymus., Results: A total of 1,306 patients were identified. Overall, 72.2% (n = 943) of thymectomies were therapeutic and 27.8% (n = 363) were nontherapeutic. The most common diagnosis in the nontherapeutic group was thymic hyperplasia (n = 174). Mortality (0.32% versus 0%; p = 0.083) and overall complication rates (25% versus 17%; p < 0.001) were higher in the therapeutic group. Patients in the nontherapeutic group were younger (median age, 41 versus 56 years; p < 0.001) and more likely to undergo a video-assisted thoracoscopic surgery thymectomy (28% versus 19%; p = 0.085)., Conclusions: In this study, 27.8% of thymectomies were nontherapeutic, and most patients underwent an open approach. The most common benign diagnosis was thymic hyperplasia, a condition for which magnetic resonance imaging has a high predictive value. Consequently, further studies are warranted to determine the optimal evaluation of patients undergoing thymectomy for presumed thymoma., (Copyright © 2014 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

The fat-rich anterior mediastinum could be a sensitive window for monitoring minute changes in vascularity induced by systemic vasculitis. To evaluate this hypothesis, an analysis of anterior mediastinal fat in patients with Behçet's disease and a control group was conducted. This study included 43 patients diagnosed with Behçet's disease within the last 11 years who underwent CT scan; 55 patients were selected as a control population. Mediastinal fat was classified according to CT morphology. Comparison of serum inflammatory markers was performed for evaluation of disease activity according to morphologic types, and average Hounsfield unit of the anterior mediastinum was measured. Significantly higher mean CT attenuation was observed in the Behçet's disease group, compared with the control group (-48.5 ± 33.5 vs. -67.7 ± 18.7, respectively, P < 0.05). Mediastinal fat types were classified as follows: pure fatty tissue (2 vs. 31 % [Behçet's disease vs. control group]), diffuse soft tissue infiltration (16 vs. 29 %), tubular structures (21 vs. 4 %), mixed infiltration with tubular structures (42 vs. 15 %), and evident thymic tissue (19 vs. 22 %). The value for mean mediastinal attenuation was significantly higher in the group with a high level of C-reactive protein than in the normal level group. The mean CT attenuation of anterior mediastinal fat is significantly higher in the Behçet's disease group, compared with the normal group. Although pathologic confirmation is needed, the cause is postulated to be either inflammatory neovascularization or minimal thymic hyperplasia induced by Behçet's disease.

Graves' thyrotoxicosis with thymic hyperplasia and pericarditis has never been described in the literature. In this case report, we present the clinical, laboratory, and radiographic findings of a 24-year-old active duty male who was admitted for management of nonexertional, positional, pleuritic chest pain. Electrocardiography confirmed pericarditis as the presenting diagnosis. Laboratory findings revealed an undetectable serum thyrotropin level and further evaluation with a contrast chest computed tomography confirmed the presence of a goiter and an anterior mediastinal mass. The patient's pericarditis and thymic hyperplasia resolved with treatment of his Graves' disease., (Reprint & Copyright © 2013 Association of Military Surgeons of the U.S.)

Aims and Background: Thymic tumors (thymomas and thymic carcinomas) represent 50% of all mediastinal tumors. Thymomas usually express high levels of somatostatin receptors, which enable in vivo imaging with 111In-DTPA-octreotide (OctreoScan®). The aim of this study was to further investigate the role of radionuclide techniques in the diagnosis, staging and follow-up of these tumors., Methods: Eight patients (5 women, 3 men, age range 35-79 years; mean ± SD 56.1 ± 15.8 years) entered the study. In 4 patients, myasthenia gravis was the presenting symptom. 111In-DTPA-octreotide scan was performed within 3 weeks after contrast enhanced CT and/or MRI. Planar and tomographic images were acquired within 24 hours of the injection of 111 MBq OctreoScan. The scintigraphic results were defined in correlation with the histological findings., Results: Histology revealed thymoma in 3 patients, thymic carcinoma in 1, insular carcinoma of presumably thymic origin in 1, thymic carcinoid in 1, and thymic hyperplasia in 2 patients. Two thymomas were at stage I, 1 thymoma and 1 thymic carcinoma at stage II, 1 insular carcinoma of presumably thymic origin at stage IV, and 1 thymic carcinoid at stage IV. OctreoScan consistently accumulated in primary and/or metastatic sites of thymic tumors while no radiotracer uptake was detected in the 2 patients with benign thymic hyperplasia. In 1 patient with a very large mediastinal mass (13 cm in largest diameter) and multiple metastatic deposits in the lungs, OctreoScan scintigraphy showed a large area of pathological uptake in the anterior mediastinum and a small area of focal uptake in the cervical-dorsal region of the right lung corresponding to a lymph node expressing somatostatin receptors., Conclusions: OctreoScan is avidly taken up by thymic tumors, enabling the diagnosis of these tumors and a better evaluation of their extension. It does not accumulate in thymic hyperplasia, thus allowing the differential diagnosis between these 2 pathological conditions. In patients affected by myasthenia gravis, OctreoScan scintigraphy can play an important role in characterizing thymic masses.

Aim: To make differential diagnosis of thymic hyperplasia and mediastinal tumor after chemotherapy (CT) in patients with Hodgkin's disease (HD)., Material and Methods: The examination of 182 HD patients aged 16-71 years (median 28 years) included chest x-ray computed tomography (XCT) at baseline, during treatment, each 3 months, ultrasound investigation of the chest and abdominal cavity. All the patients received 6-8 courses of the treatment according to the program BEACOPP-14 followed by radiotherapy on the residual tumor in 137 patients, or not followed in 45patients., Results: Soft tissue tumor in the anterior mediastinum was detected in 14 (31%) from 45 unirradiated patients (age 19-31 years, median 24 years) 1 to 10 months (median 3.5 months) after chemotherapy. The analysis of the data of ultrasound investigation and tomography identified a mediastinal lesion as thymic hyperplasia. The patients are now in remission with follow-up median 21 months (13-36 months). No recurrence was registered., Conclusion: Young HD patients with unirradiated mediastinum develop thymic hyperplasia in 31% cases within one year after chemotherapy. In view of this, detection of the lesion in the anterior mediastinum after CT demands complex examination for differential diagnosis of thymic hyperplasia with tumor recurrence to avoid unwanted intensification of the treatment.

Background: Thymic hyperplasia is associated with Graves' disease, particularly in young patients. The degree of thymic transformation is minimal in most but not all patients. In the latter group radiological measurements of thyroid size and their change with treatment have rarely been reported. We present two patients with Graves' disease and relatively rapid resolution of thymic enlargement after successful treatment of their hyperthyroidism., Summary: Three patients with thyrotoxicosis secondary to Graves' disease and marked thymic enlargement were seen at our institution during a 2-year period. On computed tomography (CT) studies their volumes were 67, 81, and 54 cm(3). Thymic hyperplasia in the setting of Graves' disease was the diagnosis of exclusion. Two of the patients returned for follow-up after successful treatment of thyrotoxicosis as requested. On repeat CT their thymic volumes had decreased by 72% and 78%, respectively. Two types of histological modifications of the thymus have been described in association with Graves' disease, namely, thymic parenchyma hyperplasia and medullary lymphoid hyperplasia. The mechanisms underlying thymic transformation in patients with Graves' hyperthyroidism are not completely elucidated, but autoimmune processes underlying Graves' disease are presumed to play a role. The clinical course of our patients is consistent with earlier literature, indicating that thymic enlargement may occur in conjunction with Graves' hyperthyroidism, and that it usually resolves as hyperthyroidism is treated, but there is little quantitative pre- and posttreatment of hyperthyroidism data., Conclusion: Although every patient must be individually considered, it appears that thymic hyperplasia can be diagnosed in most Graves' hyperthyroid patients by considering the clinical context and appropriate radiologic studies such as CT. Raising awareness of the association of thymic hyperplasia in patients with Graves' hyperthyroidism and its resolution with the reversibility of the hyperthyroid state should prevent unnecessary thymic evaluation and surgery with its attendant risks.

True thymic hyperplasia is a very rare entity. We present an instance of idiopathic true massive thymic hyperplasia in a 9-month-old girl with a very large left-sided mediastinal mass noted on diagnostic imaging. Percutaneous biopsy revealed normal thymic tissue. Steroids were administered with no response. Surgery may be required in patients with respiratory distress unresponsive to steroids., (Copyright 2010 Elsevier Inc. All rights reserved.)

An enlarged thymus adversely affected pulmonary artery development and perfusion in a 4-month-old boy with asplenia syndrome and a single ventricular circulation with aorto-pulmonary shunt. Steroid administration for 4 weeks successfully reduced thymus volume, concomitant with improvement of pulmonary vasculature and perfusion. Given the importance of pulmonary physiology in the Fontan circulation, the effects of thymic hyperplasia on pulmonary circulation should be taken into consideration in the overall management of candidates for Fontan surgery.

A 32-year-old female case of large thymic hyperplasia with hyperthyroidism is reported. A computed tomography (CT) examination disclosed a large mediastinal mass (16 x 11 cm) with a heterogeneous internal structure containing both soft tissue density areas and fat density areas. The mass was histologically diagnosed as thymic lymphoid hyperplasia. The thymic mass enlarged during hyperthyroidism and then regressed markedly after treatment with antithyroid drugs. After the thymic mass decreased by about one third of its maximum volume, the mass stopped regressing and has remained the same size for more than 6 years. A CT scan showed a decrease in the soft tissue density area and predominance of the fat density area. The potential response to antithyroid therapy must be considered before recommending resection of thymic tumors diagnosed as hyperthyroidism-related thymic hyperplasia.

Thymic hyperplasia occurs in a small proportion of patients receiving chemotherapy for various malignancies. It likely results from an immunologic rebound phenomenon. Fluorodeoxyglucose positron emission tomography-computed tomography is an important tool for staging malignant neoplasms. We report a case of rebound thymic hyperplasia manifesting as a hypermetabolic mass on fluorodeoxyglucose positron emission tomography-computed tomography after pneumonectomy and chemotherapy for primary pulmonary synovial sarcoma. We highlight the importance of recognizing the phenomenon of rebound thymic hyperplasia, as it can mimic residual or recurrent malignancy, especially in the setting of altered chest anatomy.