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Radiological profile of mediastinal masses with special reference to computed tomography.

INTRODUCTION

Computed tomography is an important procedure for detecting mediastinal masses. Computed tomography findings used to differentiate between inflammatory and neoplastic masses includes location, nature of mass (Solid, cystic, vascular), enhancement pattern, status of surrounding cystic, vascular), enhancement pattern, status of surrounding fat planes (Maintained or lost), involvement of adjacent structures, associated extramediastinal lesion, presence of calcification and fat.

ANATOMY

DIVISIONS OF THE MEDIASTINUM. (1)

It may be divided for purposes of description into two parts: an upper portion and above the upper level of the pericardium, which is named the superior mediastinum; and a lower portion, below the upper level of the pericardium. This lower portion is again subdivided into three parts, viz., that in front of the pericardium, the anterior mediastinum; that containing the pericardium and its contents, the middle mediastinum; and that behind the pericardium, the posterior mediastinum.

CONTENTS OF THE MEDIASTINUM

SUPERIOR MEDIASTINUM

It contains the origins of the Sternohyoidei and Sternothyreoidei and the lower ends of the Longi colli; the aortic arch; the innominate artery and the thoracic portions of the left common carotid and the left subclavian arteries; the innominate veins and the upper half of the superior vena cava; the left highest intercostal vein; the vagus, cardiac, phrenic, and left recurrent nerves; the trachea, esophagus, and thoracic duct; the remains of the thymus and some lymph glands.

ANTERIOR MEDIASTINUM

It contains a quantity of loose areolar tissue, some lymphatic vessels which ascend from the convex surface of the liver, two or three anterior mediastinal lymph glands, and the small mediastinal branches of the internal mammary artery.

MIDDLE MEDIASTINUM

It contains the heart enclosed in the pericardium, the ascending aorta, the lower half of the superior vena cava with the azygos vein opening into it, the bifurcation of the trachea and the two bronchi, the pulmonary artery dividing into its two branches, the right and left pulmonary veins, the phrenic nerves, and some bronchial lymph glands.

POSTERIOR MEDIASTINUM

It contains the thoracic part of the descending aorta, the azygos and the two hemiazygos veins, the vagus and splanchnic nerves, the esophagus, the thoracic duct, and some lymph glands.

FELSON'S METHOD

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In this method the anterior mediastinum includes the pericardium and its contents and lies anterior to a line extending from the posterior margin of the cardiac shadow upwards along the anterior margin of the trachea. The middle mediastinum includes all structures behind this line and anterior to a line drawn connecting a point on each vertebral body 1cm posterior to its anterior margin. The posterior mediastinum is essentially the paravertebral gutter.

AIMS AND OBJECTIVES

The study was carried out with the following aims and objectives:

* To determine the disease pattern of various mediastinal masses.

* To establish utility value of computed tomography.

* To compare the CT findings with x-ray and histopathological findings whenever possible.

MATERIAL AND METHODS

This study entitled "Radiological evaluation of mediastinal masses" was carried out at the Department of Radiodiagnosis, Netaji Subhash Chandra Bose Medical College and Hospital, Jabalpur, between the time period October 2008 to October 2009.

Study Population

The series consists of all patients (Male/female) referred to computed tomography with suspected diagnosis of mediastinal masses on radiograph. It also included patients with normal radiograph, but with strong clinical suspicion of mediastinal masses.

Equipment Used

X-ray will be done on WIPRO Dx Machine (500mAs). Patient will be scanned on the Multislice CT machine (GE BRIGHT SPEED 16 slice).

METHODS

All patients recruited in the study were examined in detail with complete history and physical examination.

* Routine hematological tests, other relevant investigations were obtained in all patients.

* Whenever possible, the diagnosis was confirmed by FNAC/Biopsy and operative findings.

CT scan of mediastinum requires imaging of the thorax into axial planes. Reformatting in coronal and sagittal planes was done using software provided.

Diagnostic images were stored on computer in jpeg version after converting the DICOM file to jpeg file using an e-film software.

OBSERVATIONS

Gender Distribution of Cases

The present study included 50 patients ranging from 1 day to 80 years of age; 74% of the patients were males in the present study, whereas only 26% of the patients were females. GM Graeber et al. (2) evaluated 42 patients. The present studies showed male predominance.

Clinical Manifestations

The patients who were referred for radiological evaluation presented with various clinical manifestations such as cough, breathlessness, fever, chest pain, dysphagia, etc. In study done by RD Pugatch et al. (3) in five patients with anterior mediastinal mass, three were asymptomatic and two complained of chest pain. The most common clinical manifestation in the present study was cough, which was present in 40 cases. The second most common clinical symptom was breathlessness, which was present in 37 cases.

Mediastinum Involved

In the present study, anterior mediastinum was the most common involved compartment followed by middle mediastinum; posterior mediastinum was least commonly involved compartment.

Classification of Mediastinal Lesions

Rebner M et al. (4) showed CT is an important modality for imaging mediastinal masses, and certain CT attenuation features (Fat, calcium or water attenuation, contrast enhancement) are well known to suggest specific diagnoses. Metastatic disease and lymphoma accounted for 69% of masses in his series. In present study primary lesions other than lymphoma accounted for 20%, whereas metastatic disease and lymphoma accounted for 80% of mediastinal masses.

Nature of the Lesions

In the study done by Massie RJ et al. (5) Thirty-one of the 55 (56%) lesions were malignant. In the study done by Wyttenbach R et al. (6) the 28 of 38 mediastinal masses were malignant. Present study included wide range of mediastinal lesions including both benign and malignant pathologies. In the present study, majority of the lesions were malignant, accounting for 72% of the total cases which was comparable to the study done by Wyttenbach R et al. (6) in whose study 74% of the lesions were malignant.

Loss of Surrounding Fat Planes

In the present study 27 out of 37(73%) malignant masses showed loss of fat planes, whereas no case of benign pathology showed obliterated fat planes.

Frequency of Lesions

In the study done by Wyttenbach R et al. (6) 45 of 59 cases (76.27%) of mediastinal and chest wall tumors in children is malignant. In the study done by Massie RJ et al. (5) thirty-one of the 55(56%) lesions were malignant in children. In present study most common mediastinal lesions were pulmonary Koch's with mediastinal lymphadenopathy and bronchogenic cyst.

In adult's most common mediastinal mass was lymph nodal metastasis from carcinoma bronchus followed by lymphoma, CA esophagus, pulmonary Koch's with mediastinal lymphadenopathy, metastasis from other primaries.

Density of Lesions on Unenhanced Scan

In the present study, all the cases of lymphoreticular malignancies (n=4) and malignant neoplastic conditions (n=33) and benign conditions (n=11) showed soft tissue attenuation on precontrast scan. Fat density was present only in 2 cases of dermoid enabling their confident diagnosis on CT. Vascular lesion was present in 1 case in the form of aortic aneurysm. Fluid density was seen in 1 case of bronchogenic cyst. In study done by Rebner M et al. (4) he showed that certain CT attenuation features (Fat, calcium or water attenuation, contrast enhancement) are well known to suggest specific diagnoses.

Pattern of Contrast Enhancement

In the present study, post contrast scan was done routinely in all patients and enhancement pattern were divided into three categories: homogeneous, heterogeneous and lesions showing no enhancement. Lymphoreticular malignancy was the commonest group to show homogeneous contrast enhancement, in which 3 out of 4 showed homogeneous enhancement whereas heterogeneous contrast enhancement with necrotic areas was seen most commonly in case of malignant lesions (n=33) and in one case of the congenital lesions no contrast enhancement was seen

Cystic or Solid Nature of Mass

Computed tomography could generally differentiate between solid or non-solid nature of mass. In present study 2 cases are of non-solid nature, which included 1 case of vascular lesions, 1 case each of bronchogenic cyst. In study conducted by GM Graeber et al. (2) 22 of 25 patients had accurate assessment as to the cystic or solid nature of the lesions (88%).

SUMMARY

* X-ray and CT scan of mediastinum were done in all 50 patients presenting with symptoms and signs of mediastinal mass.

* Detailed history with clinical examination, laboratory investigation and histopathology reports were obtained.

* X-ray and CT scans of these patients were carefully evaluated and provisional diagnosis was made.

* Diagnosis was confirmed either by histopathology or by positive response to treatment.

* The males were the predominantly affected sex in all the etiologic lesions occurring in mediastinum.

* The malignant lesions were most common. The common age of involvement pertaining to malignant lesions was 51 to 70 years of age group.

* The most common mediastinum to be involved in inflammatory as well as neoplastic lesions was anterior mediastinum and least one to get involved was posterior mediastinum.

* Neoplastic lesions in present study most commonly affected the age group of patients above 50 years.

* In present study, it was possible to diagnose malignant neoplasms by studying the loss of fat planes. The extension of these lesions was accurately depicted on computed tomography.

* Computed tomography is very specific between differentiating solid and nonsolid lesions of mediastinum.

CONCLUSIONS

1. CT scan evaluates soft tissue details of mediastinum. It is the most cost effective modality available for mediastinal evaluation.

2. Wide spectrum of disease affecting the mediastinum can be detected by CT.

3. CT has high accuracy in diagnosis of inflammatory conditions and their complications. It is also a very sensitive modality for detection, accurate localization and determination of exact extent of mediastinal neoplasms.

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Axial pre- and post-contrast image showing soft tissue attenuation mass lesion without calcification, which on contrast showing subtle enhancement with lobulated margin occupying superior and middle mediastinum suggestive of lymph node mass.

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Soft tissue density seen involving upper and middle Lt. long fields with smooth regular margins.

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Well defined cystic lesion extending from Lt. parahilar region to lateral chest wall in lung parenchyma s/o bronchogenic cyst.

BIBLIOGRAPHY

(1.) Warwick R and Williams PL. The respiratory system in Gray anatomy. Descriptive and applied. 1973: Longmans Green and Company, London.

(2.) Graeber GM, Shriver CD, Albus RA, Burton NA, Collins GJ, Lough FC and Zajtchuk R. The use of computed tomography in the evaluation of mediastinal masses. The Journal of Thoracic and Cardiovascular Surgery, Vol 91, 662-666.

(3.) Pugatch RD, Faling LJ, Robbins AH, and Spira R. CT diagnosis of benign mediastinal abnormalities. American Journal of Roentgenology, Vol 134, Issue 4, 685-694.

(4.) Rebner M, Gross BH, Robertson JM, Pennes DR, Spizarny DL, Glazer GM. CT evaluation of mediastinal masses. Comput Radiol 1987 May-Jun;11(3):103-10.

(5.) Massie RJ, Van Asperen PP, Mellis CM. A review of open biopsy for mediastinal masses. J Paediatr Child Health 1997 Jun;33(3):230-3.

(6.) Wyttenbach R, Vock P, Tschappeler H. Cross-sectional imaging with CT and/or MRI of pediatric chest tumors. Eur Radiol 1998;8(6):1040-6.

Suresh Kumar [1], Sonjjay Pande [2], Praveen Baghel [3], O. P. Bhargav [4]

[1] Assistant Professor, Department of Radiodiagnosis, N. S. C. B. Medical College, Jabalpur, Madhya Pradesh.

[2] Professor, Department of Radiodiagnosis, N. S. C. B. Medical College, Jabalpur, Madhya Pradesh.

[3] Assistant Professor, Department of Surgery, N. S. C. B. Medical College, Jabalpur, Madhya Pradesh.

[4] Assistant Professor, Department of Pathology, N. S. C. B. Medical College, Jabalpur, Madhya Pradesh.

Financial or Other, Competing Interest: None.

Submission 14-11-2015, Peer Review 15-11-2015, Acceptance 17-11-2015, Published 03-12-2015.

Corresponding Author: Dr. Suresh Kumar, F-54, Doctors Colony, Medical College Campus, Jabalpur-482003, Madhya Pradesh.

E-mail: suresh6932@gmail.com

DOI:10.14260/jemds/2015/2400
Table 1: Gender Distribution

OBSERVATIONS

Gender        Nos.  Percentage

Female        14        28
Male          36        72
Grand Total   50       100

Table 2: Age and Gender Distribution

Age Distribution   Female   Male   Total

1 to 10              0       1       1
11 to 20             2       1       3
21 to 30             1       2       3
31 to 40             1       0       1
41 to 50             4       5       9
51 to 60             4       15     19
61 to 70             1       5       6
71 to 80             1       7       8
Grand Total          14      36     50

Table 3: Etiovatholoaical Distribution of Cases

ETIOLOGY        FEMALE   MALE   TOTAL   %

Malignant         9       28     37     74%
Inflammatory      5       6      11     22%
Miscellaneous     0       2       2      4%
Grand Total       14      36     50     100%

Table 4: Age Distribution of Pathologies

Age Range     Inflammatory   Neoplastic   Misc.

1 to 10            0             0          1
11 to 20           3             0          0
21 to 30           1             2          0
31 to 40           0             1          0
41 to 50           1             8          0
51 to 60           5             14         0
61 to 70           0             5          1
71 to 80           1             7          0
Grand Total        11            37        02

Table 5: Various Mediastinal Compartments Involvement

COMPARTMENT INVOLVED   NUMBER   PERCENTAGE

Anterior                 43        86%
Middle                   30        60%
Posterior                2          4%

Table 6: Mediastinum Involved in Various Pathologies

MEDIASTINUM INVOLVED   INFLAMMATORY   NEOPLASTIC   MISC

Anterior                    11            32        0
Middle                      2             27        1
Posterior                   0             1         1

Table 7: Clinical Symptomatology of Patients

SYMPTOMS              NO. OF CASES   PERCENTAGE

Cough                      43           86%
Breathlessness             30           60%
Chest pain                 28           56%
Dysphagia                  20           40%
Fever                      20           40%
Hemoptysis                 15           30%
Hoarseness of voice        5            10%
Swelling over chest        3             6%
Pain in abdomen            2             4%
Back pain                  2             4%
Vomiting                   1             2%

Table 8: Spectrum of Benign Lesions of Mediastinum

NO. OF CASES IN          PEDIATRIC AGE GROUP    ADULTS   TOTAL
                         ([less than of equal            PERCENTAGE
                         to] 13 YRS)

Pulmonary Koch's with             0               11       84.6%
  lymphadenopathy n=11
Bronchogenic cyst n=1             1               0         7.7%
Aneurysm of aorta n=1             0               1         7.7%

Table 9: Number of Cases Studied

Authors               No. of cases

RD Pugatch et al.          49
GM Graeber et al.          42
Rebner M et al.           132
Wyttenbach R et al.        78
Motoc A et al.             38
Present Study              50
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Title Annotation:Original Article
Author:Kumar, Suresh; Pande, Sonjjay; Baghel, Praveen; Bhargav, O.P.
Publication:Journal of Evolution of Medical and Dental Sciences
Article Type:Clinical report
Date:Dec 3, 2015
Words:2322
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