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Computed tomographic evaluation of mediastinal lesions.

INTRODUCTION: Computed tomography plays a significant role in the assessment of various mediastinal pathology which were initially detected on the chest radiographs. The maximum number of cases occurred in 4th-6th decade. Mediastinal masses occurred commonly in males. In our study of 50 cases of mediastinal masses, the anterior mediastinum was the most common compartment to be involved (52%) followed by posterior mediastinum (30%) and middle mediastinum (18%). Thymic masses (26.9%), neural tumors (33.6%) and metastatic lymph node masses (44.5%) were the most common mediastinal masses in the anterior, posterior and middle mediastinal compartments respectively.

In the pediatric age group neurogenic tumour was the most common mediastinal mass. Calcification was noted in (24 %) of cases. Mass effect upon the adjacent mediastinal structures was observed in (62 %) of the cases and was predominantly noted upon the airways.

Forty three cases (86%) were histologically verified and four cases (8%) of aortic disorders were verified with conventional angiography. Totally 43 cases were verified with histopathology and angiography. With an accuracy of (94%) forty three cases CT is highly useful modality for investigation of mediastinal masses.

MATERIALS AND METHODS: The study was performed from August 2012 to February 2013 in the Department of Radio-diagnosis Konaseema Institute of Medical Sciences, Amalapuram, AP. Patients referred from Medicine, Surgery and Paediatrics were evaluated through detailed history, necessary physical examination and computed tomography was carried out using Double slice CT scan--GE. Scans were obtained with both Plain and Contrast study.

We classified our mediastinal lesions into three categories as anterior, middle and posterior mediastinal masses.

RESULTS: Our study included 50 cases of mediastinal lesions between age groups 6-76 years. The maximum number of cases occurred in 4th - 6th decade. In our study of 50 cases of mediastinal masses, the anterior mediastinum was the most common compartment to be involved with (52%) followed by posterior mediastinum (30%) and middle mediastinum (18%).

DISCUSSION: The mediastinum is a site for vast range of diseases varying considerably, ranging from tumors both benign and malignant, cysts, vascular lesions, lymph node masses and mediastinitis. Although conventional radiographs can show recognizable abnormalities in many patients with mediastinal abnormalities, in patients with mediastinal pathology radiographs are limited in their sensitivity to delineate the extent of mediastinal abnormalities and the relationship of masses to specific mediastinal structures. With computed tomography these problems are overcome because of its excellent resolution and tomographic format and therefore CT plays an important role in the evaluation of the mediastinum.

Majority of the symptoms were of non-specific nature like cough, chest pain, fever, dysphagia etc. These symptoms were mainly due to mass effect from the mediastinal lesions and were dependent on the location of the mass. Anterior mediastinal masses mostly presented with cough and dyspnea probably due to tracheal compression. Middle mediastinal lesions due to their location presented with dysphagia due to involvement of the esophagus or its compression. Neurogenic tumours account for about (9%)of primary mediastinal masses in adults, although they are more prevalent in children, constituting (29% )of mediastinal tumours. (6)

In our study, anterior mediastinal masses were found to be the commonest accounting for (52 %). Posterior mediastinal masses accounted for (36%), followed by middle mediastinal masses accounting for (20%) of the cases. The cases were analyzed in the following manner as discussed below:

A: Symptoms Distribution

Symptoms

Cough         44%
Dyspnea       36%
Fever         20%
Chest Pain    20%


In our study of 52 cases, cough was the most common clinical symptom constituting (44 %) followed by dyspnea (36%), fever (20%) and chest pain (20%).

According to the Davis study in 400 consecutive patients with mediastinal masses, chest pain constituted the most common symptom i.e. (30%), followed by fever (20%). (8)

B: Compartmental distribution of mediastinal masses

Compartment             Percentage

Anterior Mediastinum    52%
Middle Mediastinum      18%
Posterior Mediastinum   30%


In our study of 52 cases, the majority of the mediastinum masses were in the anterior mediastinum constituting (52%) followed by middle and posterior mediastinal compartment which is similar to the study conducted by Strollo in 1997 wherein anterior mediastinum constituted (50%) of the masses. (7,13)

C: Individual masses distribution (Based on the
tissue of origin).

Neural tumors    10
Thymic tumors    14
Lymphoma         6
Teratoma/GCT     2
Granuloma        16
Vascular         8
Thyroid          4


In our study Lymphoma constituted (6 %) o f the mediastinal masses which is similar to study conducted by Wychulis. (1)

Lymph nodes having a short axis of 2cm or more often reflect the presence of neoplasm, such as metastatic tumor or lymphoma, sarcoidosis or infection and should always be treated as potentially significant. Whereas in variety of non infectious and non-granulomatous inflammatory diseases they are usually smaller than 2cms. (2,3,4)

Malignant lesions have predominated in the male population while benign lesions have occurred with equal frequency in both. Majority of the benign lesions have occurred in between the 2nd and 4th decade. In case of malignancy, majority of the cases have occurred between 4th and 6th decade.

Lymphoblastic lymphoma is characterized by mass without surface lobulation involving vascular structures often associated with pleural or pericardial effusion, by systemic nodal involvement including cervical, axillary, paraaortic mesenteric and inguinal and by hepatomegaly and splenomegaly. (19)

TUBERCULOUS LESIONS: In our study, tuberculous lesions constituted (16%), which is greater in comparison to Wychulis study (i.e. 6.3%) probably due to higher prevalence of tuberculosis in comparison to the western population. (1) Our study had 3 cases of paravertebral abscess (5.6%) which was associated with vertebral body destruction. According to Im study, right paratracheal lymph node enlargement was seen in (87%) of cases whereas our study showed (60 %) involvement. Similarly in Im study 52% of the lymph node enlargement showed central areas of low attenuation with rim enhancement on contrast study. (11) Our study showed (40 %) involvement.

According to Choyke in their study on adult onset pulmonary tuberculosis, reported (40%) of adults showed presence of pleural effusion, whereas our study showed (50 %) cases of Tuberculosis associated with pleural effusion. (12)

Hilar and mediastinal lymph node enlargement is commonly seen on CT in active tuberculosis cases, more frequently in children than adults. (6)

THYMIC MASSES: Computed tomography should be the imaging method of choice following plain chest radiograph when suspected thymic abnormality require further evaluation. (5) In our study the thymic tumors formed the majority with (14%) which is similar to studies conducted by Cohen and Davis. (10, 8) In a study by Chen on 34 patients with CT diagnosis of thymic mass, thymoma constituted(91%), thymic cyst (2.9%) whereas our study of 7 patients with thymic mass, thymoma constituted(42%), and thymic hyperplasia (28%). (9)

According to Naidich, Thymoma is most commonly seen between 50-60 years which is comparable to our study in which the 3 patients with thymoma where of age 40, 48 years and 48 years respectively. (15)

THYROID MASSES: Intrathoracic goiters are a common cause of mediastinal enlargement. Thyroid masses account for 11-15 % of mediastinal masses. (14) In our study they represented only (3%) of the cases. Rounded or irregular, well defined areas of calcification may be seen in benign areas, whereas amorphous cloud like calcification is occasionally seen within carcinomas. (20)

ANEURYSM OF THORACIC AORTA: Aortic aneurysms can result in a mass in the anterior, middle or posterior mediastinum. The classical description of aortic aneurysm is an area of permanent dilatation of the aorta where the dilatation is at least 50% greater than baseline or standardized normal limits. (16)

PLEUROPERICARDIAL CYST: They result from aberrations in the formation of coelomic cavities. Pericardial cysts are invariably connected to the pericardium. Majority of them arise in the anterior cardiophrenic angle, more frequently on the right, but can be seen as high as the pericardial recesses at the level of the proximal aorta and pulmonary arteries. (17) CT shows thin walled unilocular water density (O-20HU) cystic structure. Wall may calcify.

BRONCHOGENIC CYST: Bronchogenic cysts are congenital lesions thought to result from abnormal budding of the embryonic foregut. Most cysts are located in the mediastinum, near the tracheal carina predominantly in the middle mediastinum (79%) less commonly may occur within the lung parenchyma, pleura or diaphragm (15%) according to McAdam's series. (18)

REFERENCES:

(1.) Wychulis AR, Payne WS, Clagett OT et al. Surgical treatment of mediastinal tumors: a 40 year experience. J Thorac Cardiovas Surg 1971; 62: 379-92.

(2.) Andonopoulos AP, Karadanas AH, Drosis AA et al, CT evaluation of mediastinal lymph nodes in primary Sjogren syndrome. J Comput Assist Tomogr 1988; 12: 199-201.

(3.) Abele DR, Gamsu G, Lynch D. Thoracic Manifestations of Wegener's Granulomatosis, diagnosis and course, Radiology 1990; 174: 703-9

(4.) Bergein C, Castellino RA, Mediastinal Lymph Node Enlargement on CT scans in patients with unusual interstitial pneumonitis, AJR, Am J Roentgenol 1979; 132: 1721.

(5.) Baron RL, Lee JKT, Sagel SS, Peterson RR. Computed Tomography of the normal thymus. Radiology 1982; 142: 121-5

(6.) Ribet ME, Cardot GR. Neurogenic tumors of the thorax. Ann Thor Surg 1994;58: 1091-5.

(7.) Strollo DC, Rosado de Christenson ML, Jett JR. Primary mediastinal tumors. Part I. Tumors of the anterior mediastinum. Chest 1997; 112: 511-22.

(8.) Davis et al. Primary cysts and neoplasms of the mediastinum: Recent changes in clinical presentations, methods of diagnosis, management and results. Ann Thorac Surg 1987; 44: 229-37.

(9.) Chen J, Weisbrod GL, Herman SJ. Computed tomography and pathologic correlations of thymic lesion. J Thorac Imaging 1988; 3: 61-5.

(10.) Cohen AJ, Thompson LN, Edwards FH et al. Primary cysts and tumors of the mediastinum. Ann Thorac Surg 1991; 51: 378-86.

(11.) Im JG, Itoh H, Shim YS et al. Pulmonary Tuberculosis: CT findings early active disease and sequential change with antituberculous therapy. Radiology 1993; 186: 653-60.

(12.) Choyke PL, Sostaman HD, Curtis AM et al, Adult onset pulmonary tuberculosis. Radiology 1983: 148: 357-59..

(13.) Strollo DC, Rosado de Christenson ML, Jett JR. Primary mediastinal tumors: Part II, Tumors of the middle and posterior mediastinum. Chest 1997; 112: 1344-57.

(14.) Prasad A. et al.,. Computerized tomographic evaluation of mediastinal lesions--Pictorial assay, Ind J Radiol Imag; 2001, 11:65-70.

(15.) Naidich DP, Webb WR, Muller NL, Zerhouni EA, Seigelmann SS. Mediastinum, Chapter 2 In: Naidich DP, Muller NL, Zerhouni EA, Webb WR, Krinsky GA (eds) Computed tomography and Magnetic Resonance of the thorax, 3rd edition, Lippincott Williams and Wilkins, Philadelphia, 1999: 38-160.

(16.) Nguyen BT. Computed tomography of thoracic aortic aneurysms. Seminars in Roentgenology 2001; 36 (4): 309-24

(17.) Jeung MY, Gasser B, Gangi A et al. Imaging of cystic masses of the mediastinum. Radio graphics 2002; 22: 579-93.

(18.) McAdams HP, Kirejczyk WM, Rosado de Christenson ML et al. Bronchogenic cyst: Imaging features with clinical and histopathologic correlation. Radiology 2000; 217: 441-46.

(19.) Tateishi U, Muller NL, Johkoh T et al Primary mediastinal lymphoma characteristic features of the various histological subtypes on CT. J Comput Assist Tomogr 2004; 28 (6): 782-89.

(20.) Armstrong R, Padley SPG. The mediastinum, Chapter 17 In: Grainger RG, Allison D, Adam A, Dixon AK (eds), Diagnostic radiology, Vol. 1, 4th edition, Churchill Livingstone, London, 2001: 353-76.

(21.) Gregson RHS, Whitehouse RW, Wright AR, Jenkins JPR. The mediastinum, Chapter 2 In: Sutton P (ed) Textbook of Radiology and Imaging, Vol. 1, 7th edition, Churchill Livingstone, London, 2003: 57-86.

P. S. S. Kiran, V. B. Kalra.

[1.] Senior Resident. Department of Radiodiagnosis, Konaseema Institute of Medical Sciences, Amalapuram, Andhra Pradesh.

[2.] Professor. Department of Radiodiagnosis, Konaseema Institute of Medical Sciences, Amalapuram, Andhra Pradesh.

CORRESPONDING AUTHOR:

P. S. S. Kiran, Department of Radiodiagnosis, KIMS Medical College, Amalapuram- 533201. E-mail: drpsskiran@gmail.com Ph: 0091 9490119999

CLASSIFICATION OF MEDIASTINAL MASSES- Based on Location (21)

               Common lesions                  Rare lesions

               * Tortuous brachiocephalic      *Aneurysm of
                 vein                            brachiocephalic
               * Lymph node enlargement          artery
               * Retrosternal goiter           * Lymphangioma
               * Fat deposition                * Parathyroid
               * Thymic tumour                   adenoma
               * Germ cell                     * Sternal mass
Anterior       * Epicardiac fat pad tumours    * Lipoma
mediastinum    * Diaphragmatic hump            * Haemangioma
               * Pleuropericardial cyst        * Morgagni hernia

               * Lymph node enlargement
               * Aneurysm arch aorta
Middle         * Enlarged pulmonary artery     * Tracheal lesions
mediastinum    * Dilated superior vena cava    * Cardiac tumours
                 Bronchogenic cyst

               * Neurogenic tumours            * Neurenteric cyst
               * Hiatus hernia                 * Pseudocyst of
               * Aneurysm of descending          pancreas
Posterior        artery                        * Sequestration lung
mediastinum    * Oesophageal masses            * Thoracic duct cyst
               * Dilatation of azygos vein     * Bochdalek hernia
               * Para vertebral mass           * Extramedullary
                                                 hemopoiesis
                                               * Thoracic duct cyst

Thoracic aorta passes through all the divisions of mediastinum.
Hydatid cyst can occur most commonly in the middle and posterior
mediastinum. Masses situated in all mediastinal compartments are
lymphoma and sclerosing mediastinitis

Compartmental distribution of mediastinal lesions

Compartment              No of Cases    Percentage

Anterior Mediastinum          26            52
Middle Mediastinum            9             18
Posterior Mediastinum         15            30

Anterior Mediastinal Lesions distribution

                        NO of CASES    Percentage

Thymic masses                7            26.9
Metastatic lymph Node        5            19.2
TB Lymph Node                4            15.4
Aortic Mass                  4            15.4
Lymphoma                     3            11.6
Thyroid Mass                 2             7.7
Germ cell Tumour             1             3.8
Total                        26            100

Middle mediastinal Lesions distribution

                              No of cases    Percentage

Metastatic Lymph Node              4            44.5
TB Lymph Node                      2            22.2
Neuroenteric cyst                  1            11.1
Esophageal Duplication Cyst        1            11.1
Bronchogenic cyst                  1            11.1
Total                              9             100

Posterior mediastinal lesions distribution

                           No of masses    Percentage

Neural tumors                    5            33.3
Para vertebral abscess           3             20
TB Lymph Node                    2            13.3
Oesophageal mass                 2            13.3
Hydatid cyst                     1             6.7
Para vertebral hematoma          1             6.7
Lymphangioma                     1             6.7
Total                           15             100
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Title Annotation:ORIGINAL ARTICLE
Author:Kiran, P.S.S.; Kalra., V.B.
Publication:Journal of Evolution of Medical and Dental Sciences
Article Type:Report
Geographic Code:9INDI
Date:Mar 18, 2013
Words:2210
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