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Standard Report Terms for Chest Computed Tomography Reports of Anterior Mediastinal Masses Suspicious for Thymoma

2011; Elsevier BV; Volume: 6; Issue: 7 Linguagem: Inglês

10.1097/jto.0b013e31821e8cd6

1556-1380

Edith M. Marom, Melissa L. Rosado-de-Christenson, John F. Bruzzi, Masaki Hara, Joshua Sonett, Loren H. Ketai,

Lung Cancer Diagnosis and Treatment

There is a growing demand for structured reporting in radiology and for the formulation of standard terms to be used by clinicians and radiologists alike. A study focusing on computed tomography (CT) reporting of lung nodules found inconsistency of the reporting of their margins and presence of calcifications.1Burns J Haramati LB Whitney K et al.Consistency of reporting basic characteristics of lung nodules and masses on computed tomography.Acad Radiol. 2004; 11: 233-237Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar Another study, comparing imaging terms listed in the Fleischner Society Glossary2Hansell DM Bankier AA MacMahon H et al.Fleischner Society: glossary of terms for thoracic imaging.Radiology. 2008; 246: 697-722Crossref PubMed Scopus (2189) Google Scholar with their use in medical lexicons including the International Classification of Diseases, 9th revision, Clinical Modification (Center of Medicare and Medicaid Services, Washington, DC), Systematized Nonmenclature of Medicine–Reference Terminology (SNOMED-RT) (College of American Pathologists, Northfield, IL), and the Unified Medical Language System (National Library of Medicine, Bethesda, MD), found low rates of utilization of Fleischner terms ranging from 3 to 36%.3Langlotz CP Caldwell SA The completeness of existing lexicons for representing radiology report information.J Digit Imaging. 2002; 15: 201-205Crossref PubMed Scopus (35) Google Scholar On the other hand, when standardized reporting is implemented for imaging a specific disease, such as seen in the screening for breast cancer, this leads to improved patient care. It is expected that the creation of a standardized terminology for the description of an anterior mediastinal mass suspicious for thymoma and the promotion of its use will result in improved communication between the clinician and the radiologist and will ultimately positively impact patient care. In addition to developing a common language, including pertinent information in the radiologic report that will influence therapy requires knowledge of the disease and is often disease specific. Because of this, standardized reporting has been created for specific diseases in a few organs and has been proven useful. The American College of Radiology developed the Breast Imaging Reporting and Data System4D-D'Orsi CJ Mendelson EB Ikeda DM et al.Breast Imaging Reporting and Data System: ACR BI-RADS - Breast Imaging Atlas. American College of Radiology, Reston, VA2003Google Scholar to characterize breast lesions seen on mammography and breast ultrasound in a standardized manner that correlates with the underlying histologic findings. The Breast Imaging Reporting and Data System assigns a percentage probability of malignancy to each category and has gained worldwide acceptance in its use for guiding clinical management.5Stavros AT Thickman D Rapp CL et al.Solid breast nodules: use of sonography to distinguish between benign and malignant lesions.Radiology. 1995; 196: 123-134Crossref PubMed Scopus (1386) Google Scholar A similar system has been developed for the ultrasound evaluation of thyroid nodules, stratifying them into those with imaging findings more likely to be malignant and those less likely to be malignant with suggestions for appropriate clinical management called Thyroid Imaging and Reporting Data System.6Horvath E Majlis S Rossi R et al.An ultrasonogram reporting system for thyroid nodules stratifying cancer risk for clinical management.J Clin Endocrinol Metab. 2009; 94: 1748-1751Crossref PubMed Scopus (490) Google Scholar Although there is preliminary evidence to suggest that certain imaging findings in thymoma are important for staging or prognosis, further validation will require the prospective acquisition of data, which will be facilitated by the creation of a structured radiology report. The following guidelines contain descriptors that should be included in CT reports of patients with anterior mediastinal masses in whom thymoma is considered in the differential diagnosis. Corresponding representative images are included for clarity and consistency. Pertinent negatives with regard to these descriptors are just as important. Consistent use of these descriptors will help establish a common reporting language that will be used and accepted by clinicians as they make management decisions regarding their patients with thymoma and facilitate further research. The process used in development of this document was designed to represent a broad consensus within the community of clinicians and researchers interested in thymic diseases. A core workgroup (Edith M. Marom, Melissa L. Rosado-de-Christenson, John F. Bruzzi, Masaki Hara, Joshua R. Sonett, and Loren Ketai) reviewed the existing literature as well as existing standards for chest radiology that applied or could be adapted to achieving consistency in reporting imaging findings in anterior mediastinal masses. This group drafted proposed standard report terms and definitions. These were refined at an International Thymic Malignancy Interest Group (ITMIG) Definition and Terminology workshop on November 16, 2010, which was supported by the International Association for the Study of Lung Cancer. After distribution to all ITMIG members for comment, the final document was approved and adopted by ITMIG members in February 2011. The Masaoka staging system and its variants7Blumberg D Port JL Weksler B et al.Thymoma: a multivariate analysis of factors predicting survival.Ann Thorac Surg. 1995; 60 (discussion 914.): 908-913Abstract Full Text PDF PubMed Scopus (305) Google Scholar, 8Masaoka A Monden Y Nakahara K et al.Follow-up study of thymomas with special reference to their clinical stages.Cancer. 1981; 48: 2485-2492Crossref PubMed Scopus (1347) Google Scholar have been shown to strongly correlate with prognosis, 8Masaoka A Monden Y Nakahara K et al.Follow-up study of thymomas with special reference to their clinical stages.Cancer. 1981; 48: 2485-2492Crossref PubMed Scopus (1347) Google Scholar, 9Casey EM Kiel PJ Loehrer Sr, PJ Clinical management of thymoma patients.Hematol Oncol Clin North Am. 2008; 22: 457-473Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar, 10Suster S Moran CA Histologic classification of thymoma: the World Health Organization and beyond.Hematol Oncol Clin North Am. 2008; 22: 381-392Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar yet staging is often only established postoperatively. Patients with locally advanced thymoma may receive neoadjuvant chemotherapy to enable effective resection, 9Casey EM Kiel PJ Loehrer Sr, PJ Clinical management of thymoma patients.Hematol Oncol Clin North Am. 2008; 22: 457-473Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar, 11Kim ES Putnam JB Komaki R et al.Phase II study of a multidisciplinary approach with induction chemotherapy, followed by surgical resection, radiation therapy, and consolidation chemotherapy for unresectable malignant thymomas: final report.Lung Cancer. 2004; 44: 369-379Abstract Full Text Full Text PDF PubMed Scopus (226) Google Scholar as complete resection, even of advanced disease, improves survival.7Blumberg D Port JL Weksler B et al.Thymoma: a multivariate analysis of factors predicting survival.Ann Thorac Surg. 1995; 60 (discussion 914.): 908-913Abstract Full Text PDF PubMed Scopus (305) Google Scholar, 12Elkiran ET Abali H Aksoy S et al.Thymic epithelial neoplasia: a study of 58 cases.Med Oncol. 2007; 24: 197-201Crossref PubMed Scopus (12) Google Scholar Currently, it is recommended that patients with stage III and IV thymoma should receive neoadjuvant therapy.13Falkson CB Bezjak A Darling G et al.The management of thymoma: a systematic review and practice guideline.J Thorac Oncol. 2009; 4: 911-919Abstract Full Text Full Text PDF PubMed Scopus (167) Google Scholar, 14Girard N Mornex F Van Houtte P et al.Thymoma: a focus on current therapeutic management.J Thorac Oncol. 2009; 4: 119-126Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar, 15Myojin M Choi NC Wright CD et al.Stage III thymoma: pattern of failure after surgery and postoperative radiotherapy and its implication for future study.Int J Radiat Oncol Biol Phys. 2000; 46: 927-933Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar, 16Rea F Sartori F Loy M et al.Chemotherapy and operation for invasive thymoma.J Thorac Cardiovasc Surg. 1993; 106: 543-549PubMed Google Scholar, 17Venuta F Rendina EA Longo F et al.Long-term outcome after multimodality treatment for stage III thymic tumors.Ann Thorac Surg. 2003; 76 (discussion 1872.): 1866-1872Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar, 18Venuta F Rendina EA Pescarmona EO et al.Multimodality treatment of thymoma: a prospective study.Ann Thorac Surg. 1997; 64 (discussion 1591–1592.): 1585-1591Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar Historically, mediastinal imaging has been considered to have limited value in the staging of patients with thymoma. This may have been due to the limitations of older imaging techniques and the rarity of thymoma. These factors likely influenced scientific publication and limited the number of published case studies on the imaging of thymoma, which in turn decreased the statistical power of these studies. CT is currently considered the preferred imaging modality for the initial assessment and follow-up of patients with thymoma.19Marom EM Imaging thymoma.J Thorac Oncol. 2010; 5: S296-S303Crossref PubMed Scopus (60) Google Scholar In the last decade, CT technique has improved dramatically resulting in routine rapid acquisition of thin-section slices enabling high quality image reformations in multiple planes. This resulted in improved visualization of these tumors, allowing assessment of internal lesion characteristics as well as detailed visualization of the tumor's relationship to surrounding structures. Promising studies have been published in the last decade, taking advantage of modern CT imaging techniques. These studies have shown that some CT characteristics correlate with aggressive tumor behavior and higher stage. To the best of our knowledge, only two have correlated the CT appearance of thymoma with Masaoka staging.20Marom EM Milito MA Moran CA et al.Computed tomography findings predicting invasiveness of thymoma.J Thorac Oncol. 2011; ([Epub ahead of print].)Google Scholar, 21Tomiyama N Muller NL Ellis SJ et al.Invasive and noninvasive thymoma: distinctive CT features.J Comput Assist Tomogr. 2001; 25: 388-393Crossref PubMed Scopus (85) Google Scholar, 21aPriola AM Priola SM Di Franco M et al.Computed tomography and thymoma: distinctive findings in invasive and noninvasive thymoma and predictive features of recurrence.Radiol Med. 2010; 115: 1-21Crossref PubMed Scopus (23) Google ScholarPriola AM Priola SM Di Franco M et al.Computed tomography and thymoma: distinctive findings in invasive and noninvasive thymoma and predictive features of recurrence.Radiol Med. 2010; 115: 1-21Crossref PubMed Scopus (53) Google Scholar One study assessed 50 patients with thymoma21Tomiyama N Muller NL Ellis SJ et al.Invasive and noninvasive thymoma: distinctive CT features.J Comput Assist Tomogr. 2001; 25: 388-393Crossref PubMed Scopus (85) Google Scholar, 21aPriola AM Priola SM Di Franco M et al.Computed tomography and thymoma: distinctive findings in invasive and noninvasive thymoma and predictive features of recurrence.Radiol Med. 2010; 115: 1-21Crossref PubMed Scopus (23) Google ScholarPriola AM Priola SM Di Franco M et al.Computed tomography and thymoma: distinctive findings in invasive and noninvasive thymoma and predictive features of recurrence.Radiol Med. 2010; 115: 1-21Crossref PubMed Scopus (53) Google Scholar and found that invasive thymomas were more likely to be larger and have low attenuation regions, calcifications, and lobulated and irregular contours when compared with low-stage thymomas. A later study assessed 99 patients with thymoma20Marom EM Milito MA Moran CA et al.Computed tomography findings predicting invasiveness of thymoma.J Thorac Oncol. 2011; ([Epub ahead of print].)Google Scholar and found multiple factors associated with advanced disease (stages III and IV): large size, lobulated contours, heterogeneous attenuation, calcifications, infiltration of surrounding mediastinal fat, tumor abutting ≥50% of a mediastinal structure, adjacent lung abnormalities, and pleural effusion. However, after performing multivariate analysis, larger tumor size, lobulated contours, and fatty infiltration surrounding the tumor were the only imaging findings that were likely to correlate with higher stage disease, i.e., stage III or IV.20Marom EM Milito MA Moran CA et al.Computed tomography findings predicting invasiveness of thymoma.J Thorac Oncol. 2011; ([Epub ahead of print].)Google Scholar Thymomas are classified histologically by the World Health Organization (WHO) classification. Although the clinical use of the WHO classification is debatable because of lack of adequate reproducibility and clinical predictive value that was found in some studies, 10Suster S Moran CA Histologic classification of thymoma: the World Health Organization and beyond.Hematol Oncol Clin North Am. 2008; 22: 381-392Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar several CT studies have correlated CT appearance with the WHO histologic classification. Two studies that evaluated 45 and 76 patients with thymoma22Jeong YJ Lee KS Kim J et al.Does CT of thymic epithelial tumors enable us to differentiate histologic subtypes and predict prognosis?.AJR Am J Roentgenol. 2004; 183: 283-289Crossref PubMed Scopus (123) Google Scholar, 23Tomiyama N Johkoh T Mihara N et al.Using the World Health Organization Classification of thymic epithelial neoplasms to describe CT findings.AJR Am J Roentgenol. 2002; 179: 881-886Crossref PubMed Scopus (117) Google Scholar found that lobulated and irregular tumor contours were associated with more aggressive disease, although this was not confirmed by a third study24Sadohara J Fujimoto K Muller NL et al.Thymic epithelial tumors: comparison of CT and MR imaging findings of low-risk thymomas, high-risk thymomas, and thymic carcinomas.Eur J Radiol. 2006; 60: 70-79Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar that evaluated 48 patients with thymoma. The above imaging studies are promising. In fact, some clinicians already use large tumor size, tumor heterogeneity, and tumor lobulation to help identify patients who should receive neoadjuvant therapy before attempted resection. However, much larger studies correlating the relationship of imaging findings of thymoma with its biologic behavior are needed. Such studies will have to be performed on an international basis as despite thymoma being the most common primary neoplasm of the anterior mediastinum, it only accounts for less than 1% of all adult malignancies.25Duwe BV Sterman DH Musani AI Tumors of the mediastinum.Chest. 2005; 128: 2893-2909Crossref PubMed Scopus (304) Google Scholar We believe that each CT report of a mediastinal mass suspicious for thymoma or of newly diagnosed thymoma should include the following data about the primary mass and its surrounding structures: lesion location and size in the x, y, and z axis, description of the lesion contour (smooth or lobulated), presence or absence of heterogeneous attenuation, calcifications, infiltration of surrounding mediastinal fat, and tumor abutting ≥50% of an adjacent mediastinal structure and direct invasion into a vessel lumen. The following information regarding the surrounding structures must also be included: diaphragmatic elevation (consistent with phrenic nerve involvement), adjacent lung abnormalities, pleural effusion, pleural nodule or nodules, lymph node enlargement, and findings suggestive of distant metastatic disease (i.e., lung, liver, adrenal, or peritoneal nodules). If these variables are prospectively and consistently recorded, they can be used to create a table or drop down menu to be used in future structured reports (TABLE 1, TABLE 2). In addition, if all these data are routinely captured in radiologic reports of cases of thymoma, retrospective studies could be performed using the information contained in these reports.TABLE 1Documentation of Primary Tumor CharacteristicsVariableMenu OptionSize (cm)x axis (longest dimension on axial slice)y axis (perpendicular to longest dimension)z axis (craniocaudal dimension)ContourSmoothLobulatedInternal densityHomogenousHeterogeneousCysticCalcificationYesNoInfiltration of surrounding fatYesNoAbutment of ≥50% of a mediastinal structure with loss of fat planeYes (list which structure/s)NoAdditional mediastinal structures the tumor abutsYes (list)NoDirect vascular endoluminal invasionYes (list vessel name)No Open table in a new tab TABLE 2Documentation of Involvement of Surrounding StructuresVariableMenu OptionAbnormalities in adjacent lung parenchymaYesNoPresence of a pleural effusionUnilateralBilateralNoPresence of a pleural noduleNoUnilateral/bilateral 1 2–5 >5/diffuseMediastinal lymph node enlargement (>1 cm in short axis on an axial image)Yes (list location according to node map26)NoAbutment at the expected location of the phrenic nerveYesNoElevated hemidiaphragmYesNoPresence of a pulmonary noduleYesNoExtrathoracic suspected metastasesYes (list location) No Open table in a new tab We recommend documenting the three axes of tumor size to mirror information that is consistently contained in pathology reports of excised thymomas. The axial slice chosen for measurement is that which demonstrates the longest tumor dimension. The short axis is perpendicular to the long axis on the same slice (Figure 1). Because tumor orientation does not always conform to strict sagittal or coronal reformats, the superior-inferior dimension of the tumor should be obtained by subtracting the lowest from the highest bed position in which the primary tumor is seen (Figure 1). It is expected that most of these lesions will be located in the prevascular anterior mediastinum. Some of these lesions are unilateral, whereas others cross the midline involving both sides of the mediastinum. A lesion contour is considered smooth in the absence of spiculation, ill-defined borders, or lobulation. Smooth lesions are typically spherical or ovoid in shape, but lesion contours may also conform to the shape of the adjacent mediastinum. A lobulated contour is one that exhibits one or more lobulations, characterized as convex tumor contours with adjacent notches between tumor lobules (Figure 2). Thymomas may demonstrate homogeneous or heterogeneous attenuation. Heterogeneous attenuation often manifests as areas of low attenuation within the tumor and should be assessed on soft tissue or mediastinal windows. Administration of contrast will help demonstrate tumor heterogeneity and is recommended if not contraindicated (Figure 3). Cystic thymomas exhibit intrinsic low attenuation manifesting as homogeneous water attenuation surrounded by the soft tissue tumor capsule. These lesions may also exhibit internal soft tissue septa. The presence of mural soft tissue nodules in a cystic anterior mediastinal mass is one of the characteristic manifestations of cystic thymoma. Calcifications of any pattern, including curvilinear, punctate, or coarse, have been associated with more advanced disease and should be described and characterized. Viewing the same image at a different window level, such as with bone window, may accentuate the differences between intravascular contrast and tumor calcification (Figure 4). For a tumor to be characterized as infiltrating the surrounding fat, it needs to only infiltrate the fat in one location and not necessarily along its entire circumference. Such neoplasms may exhibit irregular borders. Tumors that abut the mediastinal vessels without an intervening fat plane are not considered as infiltrating of surrounding fat, as the mediastinal fat that typically surrounds the vessel cannot be evaluated for infiltration if it cannot be visualized (Figure 5). To maintain consistency in imaging reports, vessel abutment should be described as the percentage of the vessel circumference that is touched by the adjacent tumor without an intervening tissue plane (Figure 6). Vascular invasion is rarely seen but may manifest as direct extension of the tumor into a vessel lumen (Figure 7). When present, any appreciable narrowing or deformity of the vessel lumen should be described as well. The presence and nodal stations of mediastinal lymph node enlargement should be noted in the report, 26Rusch VW Asamura H Watanabe H et al.The IASLC lung cancer staging project: a proposal for a new international lymph node map in the forthcoming seventh edition of the TNM classification for lung cancer.J Thorac Oncol. 2009; 4: 568-577Abstract Full Text Full Text PDF PubMed Scopus (745) Google Scholar as removal of any enlarged lymph nodes at surgery is recommended.27Detterbeck FC Moran CA Huang J et al.Which way is up? Policies and procedures for surgeons and pathologists regarding resection specimens of thymic malignancy.J Thorac Oncol. 2011; 6: S1730-S1738Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar The definition of mediastinal lymph node enlargement is a short-axis diameter of a lymph node greater than 1 cm on an axial image (Figure 8). Adjacent lung abnormalities such as intrapulmonary extension of tumor are rarely appreciated on CT and are usually detected intraoperatively. The most common pulmonary abnormality seen on chest CT is compressive atelectasis by the adjacent tumor, but this may be difficult to differentiate from direct extension of tumor into lung (Figure 9). Pleural effusions are not common in patients with thymoma. However, presence or absence of pleural effusions should be documented on the report as they are more frequently associated with thymic carcinoma and metastatic pleural involvement by primary neoplasms other than thymoma (Figure 9). Inclusion of the phrenic nerve in the resection may compromise pulmonary function and may lead to serious postoperative complications.28Yano M Sasaki H Moriyama S et al.Preservation of phrenic nerve involved by stage III thymoma.Ann Thorac Surg. 2010; 89: 1612-1619Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar Preoperative documentation of phrenic nerve involvement is of utmost importance as affected patients may receive preoperative chemotherapy before surgery to allow complete tumor resection of disease without resection of the phrenic nerve, thus leading to a favorable functional and survival benefit. Therefore, elevation of the hemidiaphragm should be documented in the report. In addition, tumor abutting the anatomic location of the course of the phrenic nerve should also be mentioned. The phrenic nerve courses over the brachiocephalic artery, posterior to the subclavian vein, and then crosses anterior to the hilum, over the pericardium covering the right atrium (right phrenic nerve) or left ventricle (left phrenic nerve) to the diaphragm, where it divides into branches which pierce that muscle and are distributed to its under surface (Figure 10). Metastatic thymoma typically involves the pleura and manifests as soft tissue pleural nodules that range from small lentil-shaped nodules to large pleural masses and can progress to circumferential nodular pleural thickening with involvement of the interlobar fissures. Solid pleural metastases (stage IVa) should be distinguished from pulmonary parenchymal metastases (stage IVb). Pleural nodules are disposed along the anatomic location of the pleural surfaces and are best assessed on the lung window in cases of early disease. Intraparenchymal pulmonary nodules29Huang J Detterbeck FC Wang Z et al.Standard outcome measures for thymic malignancies.J Thorac Oncol. 2010; 5: 2017-2023Crossref PubMed Scopus (107) Google Scholar are completely surrounded by lung parenchyma (Figure 11). Distant metastases are uncommon at presentation and constitute stage IVb disease. The most common site is the lung followed by the liver, lymph nodes, and bone.30Bott-Kothari T Aron BS Bejarano P Malignant thymoma with metastases to the gastrointestinal tract and ovary: a case report and literature review.Am J Clin Oncol. 2000; 23: 140-142Crossref PubMed Scopus (22) Google Scholar This article provides a lexicon of terms that should be consistently used for describing mediastinal masses suspected of representing a thymoma. Knowledge of the imaging features of high-stage thymomas as well as the correct use of these terms will add value to the CT report, will facilitate communication between clinicians and radiologists, and will allow the radiologist to play an important role in helping the clinician make management decisions for their patients with thymoma including the use of preoperative therapy. Documentation of the above imaging features of thymoma provides the basis for structured reporting and a database for collected newly diagnosed thymoma cases that permits further research.