Imaging findings of primary mediastinal yolk sac tumors / 中国医学影像技术

ABSTRACT

Objective: To explore CT and PET/CT features of primary mediastinal yolk sac tumor (PMYST). Methods: CT, PET/CT and clinical data of 14 patients with PMYST confirmed by percutaneous biopsy were retrospectively analyzed. All patients underwent plain scan and enhanced chest CT examination, while 7 patients underwent PET/CT examination. Results: CT showed round or lobulated masses in all 14 cases. The maximum diameter of masses was 4.10-13.50 cm, with an average of (10.65±2.27) cm. Lesions with the maximum diameter≥10.00 cm were in 13 cases (13/14, 92.86%).Plain CT showed non-uniform density or heterogeneous density, and the enhanced CT showed multiple strip, thin linear partition enhanced focus and flake non-enhanced area in 14 cases, among which moderate and mild enhancement were observed in 11 cases (11/14, 78.57%) and 3 cases (3/14, 21.43%), respectively. Cardiac envelope involvement was found in 5 cases (5/14, 35.71%), left cephalobrachial vein and/or superior vena cava involvement were detected in 3 cases (3/14, 21.43%), while the right upper and middle lobe involvement was noticed in 1 case (1/14, 7.14%).There were 3 patients (3/14, 21.43%) with right hilar and mediastinal lymph node metastasis, 1 (1/14, 7.14%) with right pleural metastasis and 1 (1/14, 7.14%) with right lower lung metastasis. Pericardial effusion (7/14, 50.00%) and pleural effusion (7/14, 50.00%) were found each in 7 cases, respectively. PET/CT showed markedly increased radioactivity uptake in all 7 cases. During following-up after treatment, stable or recovered well after operation were observed in 9 cases (9/14, 64.29%), whereas progressive or recurred after operation in 5 cases (5/14, 35.71%). Conclusion: The main imaging manifestations of PMYST include large round or lobulated non-uniform mass in the anterior mediastinum, often invading surrounding vessels, tissue and organs, mostly with lymph nodes and distant metastasis. The specific manifestations of PMYST are multiple strip-like, linear septate-like enhancement foci and patchy non-enhancement areas in enhanced CT. 18F-FDG uptake of the lesions are markedly hypermetabolic.