대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Thymic Carcinoma

Radiologic Findings

Chest PA shows widening of upper mediastinum. Non-contrast chest CT shows a lobulated soft tissue density mass in the anterior mediastinum. The mass invades the adjacent sternum, showing the bone destruction. Contrast enhanced CT scan shows marked enhancement of mass. Necrotic low attenuating portion is noted in lateral aspect of the mass. Focal obliteration of fat plane between the mass and left pulmonary artery is seen at the level of carina, raising the possibility of tumor invasion. A small pleural implant is noted in the right mediastinal pleura.

Brief Review

Malignant thymoma is classified into two types: type I, invasive thymoma; and typeII, thymic carcinoma. Type I malignant thymoma (invasive thymoma) behaves in a malignant fashion despite its benign histologic appearance. The distinction between ordinary thymoma and invasive thymoma dependes on the demonstration of local invasion or metastasis. Type II malignant thymoma (thymic carcinoma) is comprosied of rare tumors of the anterior mediasitnum. They are histologically malignant tumors with a clinical course that tends to be much more aggressive than that of type I malignant thymoma. Compared with thymoma, the presence of a paraneoplastic syndrome is uncommon, an associaton with myasthenia gravis was indentified in only four cases in one report published in 1993 (Arc Pathol Lab Med 1993; 117: 937). Rare cases have been associated with hypercalcemia. Radiologically, thymic carcinomas usually present as large anterior mediastinal masses that have lobulated or poorly defined margins. On CT, they can have homogeneous soft tissue attenuation or heterogeneous attenuation as a result of necrosis; foci or calcification are present in 10% to 40 % of cases. Focal or diffuse obliteration of the adjacent fat planes and evidence of extension into the pericardium or pleura is present in the majority. Although local pleural extension and associated effusion are common, distal pleural implants are seldom seen. Mediastinal lymphadenopathy is present in 40% of cases. The prognosis is poor with the 5-year survival rate of 33%. In contrast, the 5-year survival rate seen with invasive thymomas in 50-78%.

References

Keywords

Mediastinum, Malignant tumor,