Imaging Evaluation of Thymoma and Thymic Carcinoma

Abstract

Imaging is integral in the management of patients with thymoma and thymic carcinoma. At initial diagnosis and staging, imaging provides the clinical extent of local invasion as well as distant metastases to stratify patients for therapy and to determine prognosis. Following various modalities of therapy, imaging serves to assess treatment response and detect recurrent disease. While imaging findings overlap, a variety of CT, MRI, and PET/CT characteristics can help differentiate thymoma and thymic carcinoma, with new CT and MRI techniques currently under evaluation showing potential.

A Painless Right Anterior Neck Mass

“…9 Current guidelines recommend a computed tomography scan every 6 months for the first 2 years followed by annual imaging for 10 years. 4,10 The biannual screening timeline may be extended to 3 years in cases of advanced thymomas or if complete resection was not achieved. 10…”

“…The World Health Organization thymoma type is also an independent prognostic marker of recurrence-free survival but not overall survival . Current guidelines recommend a computed tomography scan every 6 months for the first 2 years followed by annual imaging for 10 years . The biannual screening timeline may be extended to 3 years in cases of advanced thymomas or if complete resection was not achieved …”

How can the rate of nontherapeutic thymectomy be reduced?

“…According to NCCN Guidelines Version 1.2021, when assessing a mediastinal mass, detection of thymic malignancy versus thymic cyst can be better discriminated with chest MRI compared to chest CT [ 20 ]. MRI has specific benefits in certain scenarios though it is not routinely used in the evaluation of thymic tumours, such as to distinguish solid from cystic lesions, to evaluate necrotic components, to evaluate enhancing septum within cystic lesions and to evaluate for areas of subtle local invasion [ 21 ]. What is more, chemical shift imaging can be utilized to detect microscopic or intravoxel fat and therefore to differentiate thymic hyperplasia and thymoma [ 15 ].…”

Invasive type B2 thymoma associated with myasthenia gravis, resection with superior vena cava reconstruction

“…In addition to CT, PET has also been described for determining invasiveness and prognosis. Tumors with a high SUVmax have an increased likelihood of carcinoma, with some studies reporting a value of 6 to predict carcinoma with high sensitivity [ 6 ]. Thymomas with higher SUVs have been thought to be associated with more invasive disease, although this has been shown to be much less predictable [ 6 ], as in this case, where the tumor had low SUV uptake despite having a high degree of invasion upon intraoperative assessment.…”