IMAGE OF THE WEEK 2014

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MEDIASTINAL TUMOURS: PART 1

The mediastinum is anatomically divided into 3 compartments: Anterosuperior compartment is the space between the sternum and pericardium, Middle or visceral compartment is bordered by the anterior and posterior pericardial reflections and finally the posterior compartment which is the region behind the posterior pericardial reflection which includes the paravertebral gutter.

Tumours occurring in these mediastinal compartments are predictable to some degree with some occurring more frequently in certain compartment then the others as shown in table 1. Tumours occurring in the middle compartment then to be benign epithelial cyst either of bronchogenic or pericardial origin while neural tumours are more likely in the posterior compartment.

Overall the most common tumours are neurogenic (20%), thymomas (20%), primary cyst (20%), lymphomas (13%), and germ cell tumours (10%). 25-40% of mediastinal tumours are malignant with majority occurring in the anterosuperior compartment and patients then to be younger, with ages between 10 – 40 years old. Neurogenic tumours and non-Hodgkin’s lymphomas are the most common tumours in children.

Majority of patients (60%) with mediastinal tumours usually present with chest pain, cough and fever.  A third of patients are asymptomatic and is usually a good indicator that the tumour is likely to be benign. Rapid tumour growth with mediastinal structures compression or invasion is usually a bad sign indicating malignant tumours as in this case of a large teratoma with malignant yolk sac tumour component. Patient can also present with paraneoplastic syndromes such as Cushing’s syndrome, thyrotoxicosis, hypertension, hypercalcaemia, hypoglycaemia, diarrhea and gynaecomastia.

A chest radiograph will usually showed an enlarged and widened mediastinum, indicating increased mediastinal tissue density. There may be calcification. CT scan of the thorax will usually confirmed the presence of a mediastinal tumour, the presence of chestwall invasion, multiple masses or extension into the spinal column. MRI is more accurate for vascular involvement and intracardiac pathology. Echocardiography is useful for patients with middle compartment tumours to differentiate between intracardiac and pericardial pathologies. Confirmation of the tumours required tissue biopsies which can be obtained via radiological route with FNAC or open biopsies via mediastinotomy incisions.

Germ cell tumours comprise of 15-25% of anterior mediastinal masses, occurring commonly in children and young adults. Germ cell tumours include teratomas, teratocarcinomas, seminomas, embryonal cell carcinomas, choriocarcinomas, and endodermal cell or yolk-sac tumours. This particular case is one of germ cell tumour with a large matured teratoma and a small component of yolk cell tumour. About 60% are benign and 40% malignant. Teratomas are predominantly benign tumours with well differentiated bone, cartilage, nerve or glandular tissue. Malignant teratomas are differentiated upon histologic identification of embryonic tissue.

Malignant tumours consist of 40% seminomas and 60% non-seminomas such as embryonal cell, choriocarcinoma, yolk-sac and teratocarcinoma.

Images and text contributed by

Mr William Chong, Department of General Surgery,RIPAS Hospital.

All images are copyrighted and property of RIPAS Hospital.