Carcinoma of the Mediastinum

Mediastinal tumors are benign or cancerous growths that form in the area of the chest that separates the lungs. This area, called the mediastinum, is surrounded by the breastbone in front, the spine in back, and the lungs on each side. The mediastinum contains the heart, aorta, esophagus, thymus and trachea.

• The anterior (front)
• The middle
• The posterior (back)

Mediastinum tumors are mostly made of reproductive (germ) cells or develop in thymic, neurogenic (nerve), lymphatic or mesenchymal (soft) tissue.

Carcinoma of the Mediastinum

Introduction
Occasionally, the biopsy diagnosis in a patient with a mediastinal tumor is "poorly differentiated carcinoma." This diagnosis poses difficult problems for the clinician, because it indicates a tumor with no histopathologic features specific enough to allow identification of the site of origin. Patients with poorly differentiated carcinoma in the mediastinum are sometimes assumed to have metastatic lung cancer with an undetectable primary lesion and are, therefore, assumed to be unresectable and incurable. In this setting, palliative radiation therapy is often administered. However, this approach is no longer adequate, because further clinical and pathologic evaluation can establish a definitive diagnosis with specific therapeutic implications in some of these patients. In addition, some patients with poorly differentiated carcinoma involving the mediastinum are curable with intensive cisplatin-based chemotherapy.

Pathologic Evaluation
Critical pathologic evaluation of mediastinal tumors is essential, because a variety of neoplasms with specific therapeutic implications can arise in this location (eg, mediastinal germ cell tumor, lymphoma, thymoma). In addition, effective therapy also exists for some neoplasms that commonly metastasize to the mediastinum (eg, small-cell lung cancer). Following light microscopic examination of an adequate biopsy specimen, immunoperoxidase staining and electron microscopy are useful in distinguishing between the various neoplasms occurring in the mediastinum. By using these methods, lymphoma and neuroendocrine tumors (including small-cell lung cancer) can be reliably identified, and appropriate therapeutic approaches can be defined. Molecular genetic analysis should also be performed, if possible, because identification of an i(12p) chromosomal abnormality is diagnostic of a germ cell tumor.