Skip Navigation LinksHome > July 2011 - Volume 6 - Issue 7 > Standard Report Terms for Chest Computed Tomography Reports...
Journal of Thoracic Oncology:
doi: 10.1097/JTO.0b013e31821e8cd6
ITMIG Definitions and Policies

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

Marom, Edith M. MD*; Rosado-de-Christenson, Melissa L. MD†‡; Bruzzi, John F. FFRRCSI§; Hara, Masaki MD∥; Sonett, Joshua R. MD¶; Ketai, Loren MD#

Free Access
Article Outline
Collapse Box

Author Information

*Department of Radiology, The University of Texas, M. D. Anderson Cancer Center, Houston, Texas; †University of Missouri-Kansas City, Kansas City, Missouri; ‡Department of Radiology, Uniformed Services University, Bethesda, Maryland; §Department of Radiology, Galway University Hospitals (GUH), Galway, Ireland; ∥Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan; ¶Thoracic Surgery Department, Columbia University New York-Presbyterian Hospital, New York, New York; and #Department of Radiology, University of New Mexico Health Science Center, Albuquerque, New Mexico.

Disclosure: The authors declare no conflicts of interest.

Address for correspondence: Edith M. Marom, MD, Department of Radiology, The University of Texas, M. D. Anderson Cancer Center, Unit 1478, 1515 Holcombe Blvd, Houston, TX 77030-4009. E-mail: emarom@mdanderson.org

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.1 Another study, comparing imaging terms listed in the Fleischner Society Glossary2 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%.3 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 System4 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.5 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.6

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.

Back to Top | Article Outline

METHODS

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.

Back to Top | Article Outline
Review of Existing Studies

The Masaoka staging system and its variants7,8 have been shown to strongly correlate with prognosis, 8–10 yet staging is often only established postoperatively. Patients with locally advanced thymoma may receive neoadjuvant chemotherapy to enable effective resection, 9,11 as complete resection, even of advanced disease, improves survival.7,12 Currently, it is recommended that patients with stage III and IV thymoma should receive neoadjuvant therapy.13–18 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.19 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.20,21,21a One study assessed 50 patients with thymoma21,21a 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 thymoma20 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.20

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, 10 several CT studies have correlated CT appearance with the WHO histologic classification. Two studies that evaluated 45 and 76 patients with thymoma22,23 found that lobulated and irregular tumor contours were associated with more aggressive disease, although this was not confirmed by a third study24 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.25

Back to Top | Article Outline

RECOMMENDATIONS

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 (Tables 1 and 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 1
Table 1
Image Tools
Table 2
Table 2
Image Tools
Back to Top | Article Outline
Definitions of Thymoma Report Terms
Primary Tumor Size

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).

Figure 1
Figure 1
Image Tools
Back to Top | Article Outline
Location

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.

Back to Top | Article Outline
Contour

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).

Figure 2
Figure 2
Image Tools
Back to Top | Article Outline
Attenuation

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.

Figure 3
Figure 3
Image Tools
Back to Top | Article Outline
Calcifications

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).

Figure 4
Figure 4
Image Tools
Back to Top | Article Outline
Infiltration of Surrounding Mediastinal Fat

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).

Figure 5
Figure 5
Image Tools
Back to Top | Article Outline
Tumor Abutting ≥50% of Mediastinal Structure

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).

Figure 6
Figure 6
Image Tools
Back to Top | Article Outline
Direct Vascular Invasion

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.

Figure 7
Figure 7
Image Tools
Back to Top | Article Outline
Mediastinal Lymph Node Enlargement

The presence and nodal stations of mediastinal lymph node enlargement should be noted in the report, 26 as removal of any enlarged lymph nodes at surgery is recommended.27 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).

Figure 8
Figure 8
Image Tools
Back to Top | Article Outline
Adjacent Lung Abnormalities

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).

Figure 9
Figure 9
Image Tools
Back to Top | Article Outline
Pleural Effusion

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).

Back to Top | Article Outline
Diaphragmatic Elevation

Inclusion of the phrenic nerve in the resection may compromise pulmonary function and may lead to serious postoperative complications.28 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).

Figure 10
Figure 10
Image Tools
Back to Top | Article Outline
Pleural Nodules

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 nodules29 are completely surrounded by lung parenchyma (Figure 11).

Figure 11
Figure 11
Image Tools
Back to Top | Article Outline
Distant Metastases

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.30

Back to Top | Article Outline

CONCLUSION

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.

Back to Top | Article Outline

REFERENCES

1.Burns J, Haramati LB, Whitney K, et al. Consistency of reporting basic characteristics of lung nodules and masses on computed tomography. Acad Radiol 2004;11:233–237.

2.Hansell DM, Bankier AA, MacMahon H, et al. Fleischner Society: glossary of terms for thoracic imaging. Radiology 2008;246:697–722.

3.Langlotz CP, Caldwell SA. The completeness of existing lexicons for representing radiology report information. J Digit Imaging 2002;15(Suppl 1):201–205.

4.D-D'Orsi CJ, Mendelson EB, Ikeda DM, et al. Breast Imaging Reporting and Data System: ACR BI-RADS - Breast Imaging Atlas. Reston, VA, American College of Radiology, 2003.

5.Stavros AT, Thickman D, Rapp CL, et al. Solid breast nodules: use of sonography to distinguish between benign and malignant lesions. Radiology 1995;196:123–134.

6.Horvath 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;94:1748–1751.

7.Blumberg D, Port JL, Weksler B, et al. Thymoma: a multivariate analysis of factors predicting survival. Ann Thorac Surg 1995;60:908–913; discussion 914.

8.Masaoka A, Monden Y, Nakahara K, et al. Follow-up study of thymomas with special reference to their clinical stages. Cancer 1981;48:2485–2492.

9.Casey EM, Kiel PJ, Loehrer PJ Sr. Clinical management of thymoma patients. Hematol Oncol Clin North Am 2008;22:457–473.

10.Suster S, Moran CA. Histologic classification of thymoma: the World Health Organization and beyond. Hematol Oncol Clin North Am 2008;22:381–392.

11.Kim 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;44:369–379.

12.Elkiran ET, Abali H, Aksoy S, et al. Thymic epithelial neoplasia: a study of 58 cases. Med Oncol 2007;24:197–201.

13.Falkson CB, Bezjak A, Darling G, et al. The management of thymoma: a systematic review and practice guideline. J Thorac Oncol 2009;4:911–919.

14.Girard N, Mornex F, Van Houtte P, et al. Thymoma: a focus on current therapeutic management. J Thorac Oncol 2009;4:119–126.

15.Myojin 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;46:927–933.

16.Rea F, Sartori F, Loy M, et al. Chemotherapy and operation for invasive thymoma. J Thorac Cardiovasc Surg 1993;106:543–549.

17.Venuta F, Rendina EA, Longo F, et al. Long-term outcome after multimodality treatment for stage III thymic tumors. Ann Thorac Surg 2003;76:1866–1872; discussion 1872.

18.Venuta F, Rendina EA, Pescarmona EO, et al. Multimodality treatment of thymoma: a prospective study. Ann Thorac Surg 1997;64:1585–1591; discussion 1591–1592.

19.Marom EM. Imaging thymoma. J Thorac Oncol 2010;5:S296–S303.

20.Marom EM, Milito MA, Moran CA, et al. Computed tomography findings predicting invasiveness of thymoma. J Thorac Oncol 2011 [Epub ahead of print].

21.Tomiyama N, Muller NL, Ellis SJ, et al. Invasive and noninvasive thymoma: distinctive CT features. J Comput Assist Tomogr 2001;25:388–393.

21a.Priola 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;115:1–21.

22.Jeong 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;183:283–289.

23.Tomiyama 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;179:881–886.

24.Sadohara 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;60:70–79.

25.Duwe BV, Sterman DH, Musani AI. Tumors of the mediastinum. Chest 2005;128:2893–2909.

26.Rusch 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;4:568–577.

27.Detterbeck 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–S1738.

28.Yano M, Sasaki H, Moriyama S, et al. Preservation of phrenic nerve involved by stage III thymoma. Ann Thorac Surg 2010;89:1612–1619.

29.Huang J, Detterbeck FC, Wang Z, et al. Standard outcome measures for thymic malignancies. J Thorac Oncol 2010;5:2017–2023.

30.Bott-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;23:140–142.

Cited By:

This article has been cited 2 time(s).

Journal of the National Comprehensive Cancer Network
Thymomas and Thymic Carcinomas Clinical Practice Guidelines in Oncology
Ettinger, DS; Riely, GJ; Akerley, W; Borghaei, H; Chang, AC; Cheney, RT; Chirieac, LR; D'Amico, TA; Demmy, TL; Govindan, R; Grannis, FW; Grant, SC; Horn, L; Jahan, TM; Komaki, R; Kong, FMS; Kris, MG; Krug, LM; Lackner, RP; Lennes, IT; Loo, BW; Martins, R; Otterson, GA; Patel, JD; Pinder-Schenck, MC; Pisters, KM; Reckamp, K; Rohren, E; Shapiro, TA; Swanson, SJ; Tauer, K; Wood, DE; Yang, SC; Gregory, K; Hughes, M
Journal of the National Comprehensive Cancer Network, 11(5): 562-576.

Journal of the National Comprehensive Cancer Network
The International Thymic Malignancy Interest Group
Detterbeck, FC
Journal of the National Comprehensive Cancer Network, 11(5): 589-593.

Back to Top | Article Outline
Keywords:

Thymoma; Computed tomography; Structured reporting; Staging

© 2011International Association for the Study of Lung Cancer

Login

Article Tools

Images

Share

Search for Similar Articles
You may search for similar articles that contain these same keywords or you may modify the keyword list to augment your search.

Other Ways to Connect

Twitter
twitter.com/JTOonline

 



Visit JTO.org on your smartphone. Scan this code (QR reader app required) with your phone and be taken directly to the site.

 For additional oncology content, visit LWW Oncology Journals on Facebook.