Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Thymic Carcinoma, Squamous cell type
- Radiologic Findings
- Chest CT scan at level of trachea shows well-enhanced and ill-defined anterior mediastinal mass which shows direct invasion into lumen of superior vena cava and encasement of right innominate artery.
CT scan at level of lower lung zone shows pleural implants in left mediastinal pleural space near aortic hiatus and posterior pleural space with pleural effusion.
CT scan at level of upper abdomen shows a mass in left retrocrural space, showing invasion to crus.
Lung window setting image shows a metastatic nodule with spiculated margin in left upper lobe. Another multiple metastatic pulmonary nodules were observed in both lungs.
- Brief Review
- The different subtypes of thymic carcinoma include squamous cell, lymphoepithelioma like, undifferentiated, small cell, basaloid, sarcomatoid, clear cell, mucoepidermoid and adenocystic.
None of the thymic carcinoma that has been reported was associated with myasthenia gravis or other systemic manifestations, which usually may be associated with thymoma.
Thymic carcinoma can grow locally to invade surrounding mediastinal structures.
The tumor can dissect along the outer aspect of the parietal pleura to affect the chest wall, diaphragm, and distant portions of the mediastinum.
Spread may also occur along the intrapleural space leading to distant pleural seeding.
Transdiaphragmatic routes of spread, direct spread and distant metastases often occur as a result of hematogenous and lymphatic invasion.
Metastases to distant extrathoracic sites such as the liver, bone, lymph node, kidneys and brain occur rarely in the late clinical course.
Differentiation between invasive thymoma and thymic carcinoma is difficult on the basis of CT findings.
However, thymic carcinomas show a higher rate of mediastinal lymph node and distant metastases than invasive thymoma. Pleural implants in thymic carcinoma are relatively rare in comparison to those in invasive thymoma.
Anterior mediastinal lymphoma, malignant germ cell tumor, carcinoid and metastasis should be included in the differential diagnosis.
The prognosis is poor with the 5-year survival rate of 33%. In contrast, the 5-year survival rate seen with invasive thymomas is 50-78%.
- References
- 1. Do YS, Im JG, Lee BH et al. CT findings in malignant tumors of thymic epithelium. J Comput Assist Tomogr 1995; 19:192-197
2. Lee EJ, Jung GS, Kim SM, et al. CT differentiation of invasive thymoma and thymic carcinoma. J Korean Radiol Soc 1998; 39:941-946
3. Wick MR, Wiland LH, Schiethauer BW, Bernatz PE. Primary thymic carcinoma. Am J Surg Pathol 1982; 6:613-630
- Keywords
- Mediastinum, Malignant tumor,