During its development, thymic primordia arise from the third and fourth pharyngeal pouches, become cylindrical, form the thymopharyngeal ducts, and descend into the anterior mediastinum. On the 8th gestational week, the thymic primordia fuse at their lower poles and on the 14th to 16th weeks, the thymus further differentiates into cortical and medullary components [ 25 ].
ETT may be found in various locations according to the path of descent [ 25 ] and anywhere in the mediastinum, mainly around the thymus. Imaging modalities of ETT include ultrasound US in infants, bearing the advantages of short examination time, high resolution, and the lack of ionizing radiation [ 27 ].
US features of ETT include echogenic linear structures, which may refer to connective tissue septa [ 28 ]. On MRI, ETT appears homogenous, isointense, or slightly hyperintense compared with muscle on T1 weighted images and hyperintense on T2 weighted images [ 29 ]. All THAs are considered malignant, due to their invasive and metastatic potential, and thus should be surgically resected in every case.
Myasthenia Gravis and Thymoma
In terms of surgical or nonsurgical treatment planning, precise staging is one of the most important factors. Performing a complete resection of not only the gland itself but also surrounding tissues containing thymic cells and lymph nodes is of utmost importance. Incomplete resection is associated with a high-recurrence rate and poor prognosis. Throughout the years several surgical methods have been described for the resection of THAs. The traditional approach is the median sternotomy.
These techniques include VATS thymectomy from both sides, cervical thymectomy, subxiphoidal thymectomy, uniportal thymectomy, and robotic resection. VATS thymectomy is a radical and expansively used minimally invasive technique in the successful removal of not only the gland but also surrounding thymic tissue [ 30 ]. Imaging evaluation of the thymus comprises many obstacles, mainly due to the fact that there are changes in size, shape, consistency, and amount of fat with age to the organ.
Precise diagnosis and differentiation between each thymic condition through imaging are essential for ideal surgical treatment planning and avoiding overtreatment. While CT remains the cornerstone of thymic imaging, MRI evolves as a useful problem-solving modality for evaluation of various thymic conditions and may remarkably support CT in everyday clinical practice, especially in cases accompanied by MG in combination with different types of the THAs or TC.
CT combined with PET imaging can be effectively used in the diagnosis of advanced THAs or TC, with control of regression after neoadjuvant treatment, thus facilitating the rate of surgical success.
With the adding of chemical shift sequence, MRI maintains a higher accuracy in distinguishing THAs from TH which is essential in the algorithm of treatment planning and deciding whether surgery is needed. In terms of neoplastic conditions, MRI proved to be an accurate modality in differentiating high- and low-risk thymomas and can be helpful in separating THA from TC. Distinguishing among various thymoma subtypes on imaging is fundamental for further treatment planning preoperative chemo- and radiotherapy or primary surgical resection and achieving total remission.
It would be beneficial if the new proposed TNM and regional N-stage classification for TETs could be more accurately described by preoperative imaging similarly to the current N-stage system for lung cancer, thus contributing to more precise clinical classification.
The Thymus Gland - Diagnosis and Surgical Management | Kyriakos Anastasiadis | Springer
Treating patients with MG is one of the mainstays of thymic surgery. Total removal of the thymus and the resection of ETT in typical locations perithymic fat, aortopulmonary window, cervical region, right and left pericardiophrenic fat, and aortocaval groove are of paramount importance in banishing MG. Preoperative imaging could be extremely helpful in discovering possible ectopic thymic foci. National Center for Biotechnology Information , U. Contrast Media Mol Imaging. Published online Jan Author information Article notes Copyright and License information Disclaimer. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article has been cited by other articles in PMC. Abstract Accurate imaging of the thymus is essential in the diagnosis and surgical treatment of both neoplastic and nonneoplastic conditions. Introduction Accurate diagnostic imaging is of great importance in the treatment management of thymic pathologies. Thymic Hyperplasia or Thymoma The rate of unnecessary or nontherapeutic thymectomies carried out according to a previous CT diagnosis is MRI In recent years MRI has integrated two important sequences into its armamentary, namely, fat suppression and chemical shift imaging.
Thymoma In cases where the diagnosis of THA is obvious and an absolute indication for thymectomy is obtained, the most important factor for the surgeon is the radio-clinicopathological data concerning the THA. Embryology of Ectopic Thymic Tissue During its development, thymic primordia arise from the third and fourth pharyngeal pouches, become cylindrical, form the thymopharyngeal ducts, and descend into the anterior mediastinum. Prevalence and Imaging Techniques of Ectopic Thymic Tissue ETT may be found in various locations according to the path of descent [ 25 ] and anywhere in the mediastinum, mainly around the thymus.
Surgical Point of View of Thymectomy All THAs are considered malignant, due to their invasive and metastatic potential, and thus should be surgically resected in every case. Summary and Outlook Imaging evaluation of the thymus comprises many obstacles, mainly due to the fact that there are changes in size, shape, consistency, and amount of fat with age to the organ. Competing Interests The authors have no conflict of interests to declare. References 1. Ackman J. High rate of unnecessary thymectomy and its cause. Can computed tomography distinguish thymoma, lymphoma, thymic hyperplasia, and thymic cysts?
European Journal of Radiology.
Diagnosis and Surgical Management
Popa G. Updates in MRI characterization of the thymus in myasthenic patients.
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Journal of Medicine and Life. Chemical shift and fat suppression magnetic resonance imaging of thymus in myasthenia gravis. Canadian Journal of Neurological Sciences. Priola A.
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Comparison of CT and chemical-shift MRI for differentiating thymoma from non-thymomatous conditions in myasthenia gravis: value of qualitative and quantitative assessment. Clinical Radiology.
Higuchi T. Thymic lesions in patients with myasthenia gravis: characterization with thallium scintigraphy. El-Bawab H. Role of flourine fluorodeoxyglucose positron emission tomography in thymic pathology.
European Journal of Cardio-Thoracic Surgery. Rosai J. Detterbeck F. Thymic tumors. Annals of Thoracic Surgery. Myasthenia gravis is a disease of the junctions where nerves that control muscle function meet the muscles themselves the neuromuscular junction. In myasthenia gravis patients, antibodies form within the neuromuscular junction that make the transmission of nerve impulses from nerve to muscle less efficient.
This creates a variety of problems which may include weakness of the peripheral muscles usually worsening with repetitive contraction of the muscles , droopy eyelids ptosis , double vision, and swallowing or breathing difficulties. Drug therapy, which usually is initiated with pyridostigmine mestinon alone, often helps these symptoms of myasthenia gravis.
Other immunosuppressive drugs, such as prednisone or azathioprine, are added in some cases. A variety of types of lymphomas tumors of the lymphatic, or lymph node, system may arise primarily in the mediastinum. These are most often located in the anterior mediastinum, but they may also involve the middle mediastinum. However, prompt and accurate pathologic diagnosis by surgical biopsy is the essence of successful therapy, and Stanford surgeons are experienced in all of the techniques available to biopsy mediastinal masses.
These minimally invasive procedures may include anterior mediastinotomy Chamberlain Procedure , mediastinoscopy, and occasionally video-assisted thorascopic surgery VATS. The availability at Stanford of the video mediastinoscope — useful from either the cervical or anterior approaches — permits accurate tissue sampling with minimal morbidity. If you would like to make an appointment to see one of our surgeons for any of these problems, please call and ask for the Thoracic Surgery new patient coordinator, or call For new patient Thoracic Surgery Clinic Scheduling, please call Clinical Instructorships Current Clinical Instructors.
Overview of the Mediastinum. Regions of the Mediastinum and Common Conditions. The mediastinum is generally considered to include three distinct regions : the anterior or anterosuperior mediastinum , the middle mediastinum, and the posterior mediastinum. The anterior mediastinum contains the thymus gland and thus is the usual location for thymomas tumors of the thymus.
Other common tumors of the anterior mediastinum are lymphomas tumors of the lymph node system and germ cell tumors tumors originating in cells similar to testicular or ovarian cells but which are located abnormally in the chest. An exciting, intensive course designed for the future leaders in our profession in the Asia-Pacific region. General European grant scheme information highlighting the main objectives, available funding and target audiences. Guides for Patients are designed to assist patients, their relatives and caregivers to better understand the nature of different types of cancer and evaluate the best available treatment choices.
Video interviews and articles designed to help patients, policy makers and other non-medical professionals better understand the principles of personalised cancer medicine. Now available in Romanian, our Guide for Patients with Advanced Cancer is designed for patients, their family members and oncologists. The objective of this ESMO-led study is to provide health authorities with data on the availability of licensed anti-neoplastic medicines. ESMO seeks to eradicate cancer at its earliest stages through effective cancer prevention awareness and advocacy campaigns.
Rare Cancers Europe is a multi-stakeholder initiative dedicated to putting rare cancers firmly on the European policy agenda. Girard, E. Ruffini, A. Marx, C. Faivre-Finn, S. Thymic epithelial tumours are a group of rare thoracic cancers including thymomas and thymic carcinomas, with a reported annual incidence of 1. These new ESMO Clinical Practice Guidelines on thymic cancer provide information on the current management of the disease including recommendations diagnosis, staging and risk assessment and management of resectable and advanced disease.
Careers at ESMO. ESMO Oncology Journals Our journals offer ESMO members and the oncology community a globally visible platform to publish scientific studies, and a highly credible source of educational updates. See where we'll be next! Find our more here. Melanoma Cutaneous Melanoma.