대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Mediastinal Seminoma

Radiologic Findings

Huge multilobulated margined mass in anterior and middle mediastinum with mass effect or invasion & narrowing of cardiovascular and airway structures. Especially marked narrowing of left mainstem bronchus and milder narrowing of right mainstem bronchus is seen. The mass shows focally necrotic portions. Small amount of pericardial effusion is seen. A few small irregular metastatic nodules in RUL subpleural zone with fissural thickening. Interlobular septalt hickenings in RUL and RML suggesting lymphangitic metastasis.

Brief Review

Mediastinal seminomas represent 3-4% of all mediastinal tumors and 40% of malignant germ cell tumors. These tumors almost exclusively affect men in the third to fourth decades. CT scans in patients with mediastinal seminomas show a large mass with sharply demarcated borders and homogeneous attenuation, indistinguishable from lymphomas. In some cases, seminomas contained small areas of low-density, making up less than 25%. Calcification is rare. Chest wall invasion is an unusual finding for seminomas. Pleuropericardial effusion also is an uncommon finding. Metastasis to regional lymph nodes, lung, bone, and liver occasionally occur. Mediastinal seminomas are highly sensitive to both radiation and systemic chemotherapy.

Non-seminomatous germ cell tumor generally grow rapidly, causing compression and invasion of mediastinal structures in young adult men. 85-95% of NSGCT patients have at least one metastatic site at presentation. Non-seminomatous tumors contain extensive central areas of near-water density on CT scans, indicating cyst formation and/or necrosis. The tumor markings had a tendency for infiltration with spiculated borders and fat plane obliteration. Pleuropericardial effusion is common.

Thymic Hodgkin disease typically manifests as multiple rounded lymph nodes that frequently affect contiguous prevascular and paratracheal nodal groups. Mediastinal HD may manifest as a discrete primary thymic mass or as a dominant bulky mass of lymph nodes. CT may show mass effect on or invasion of vital mediastinal and other adjacent structures including pleura, lung, or chest wall. Masses typically show homogeneous attenuation, but large tumos may show heterogeneous lesions. Mediastinal large cell lymphomas can present as a mass in the thymus with or without lymph node involvement. Large cell lymphoma of mediastinum is usually restricted to the intrathoracic region at the time of initial presentation. The tumors has grossly invasive features. On CT scans, the enlarged nodes in any of the malignant lymphomas may be discrete or matted together, and their edges may be well- or ill-defined. In general, they show only minor enhancement.

Most thymic carcinoid tumors produce no symptoms. This tumor is somewhat more aggressive than thymoma, being malignant in most cases, and SVC obstruction is much more common with thymic carcinoid than thymoma. Regional lymph nodes and distant metastases are reported in up to 73% and can occur late. Imaging findings are not specific and similar to other thymic tumors. This tumors usually appear as a well circumscribed mass or may obliterate contiguous fat planes. However, thymic carcinoid must be suspected when thymic mass is associated with clinical and laboratory findings of endocrine dysfunction.

Thymic carcinomas manifest as large, ill defined, infiltrative anterior mediastinal masses and are frequently associated with pleural and pericardial effusions. Pleural implants are uncommon and they are locally invasive and frequently metastasizes to regional lymph nodes and distant sites. Thymic carcinoma may exhibit cystic changes.

References

1. Strollo DC, Rosado-de-Christenson ML. Tumors of the thymus. J Thoracic Imaging 1999; 14: 152-171

2. Rosado-de-Christenson ML, Templeton PA, Moran CA. Mediastinal germ cell tumors: radiologic and pathologic correlation. Radiographics 1992; 12: 1013-30.

3. Strollo DC, Rosado-de-Christenson ML, Jett JR. Primary mediastinal tumors. Part 1. Chest 1997; 112: 511-522

4. Lee KS, Im JG, Han CH. Malignant primary germ cell tumors of the mediastinum: CT features. AJR 1989; 153: 947-951

Keywords

Mediastinum, Malignant tumor,