PMC8794359_01
Radiological images. (A) Computed tomographic (CT) scan with contrast enhancement 8 years before surgery showed a 30-mm cystic lesion with a thickened wall (arrow) and a small solid nodular lesion adjacent to the cyst (arrowhead); (B) preoperative CT scan with contrast enhancement showed that the solid nodule adjacent to the cyst increased in size (arrowhead) whereas the size of the cyst did not change (arrow) compared with those 10 years ago; (C) preoperative 18F-fluorodeoxyglucose positron emission tomography scan showed that the solid nodule adjacent to the cyst had high metabolic activity (the maximum standard uptake value 12.1) (arrowhead) whereas there was no abnormal metabolic activity in the cyst (allow); (D) timeline of follow-up evaluations and treatment for the thymic cyst and adjacent nodule.
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A 65-year-old man with no significant past medical history was found to have a thymic cystic nodule in a chest computed tomography (CT) scan (Figure 1A). The patient was followed-up with annual CT scans, which showed a growing solid nodule adjacent to the known thymic cyst (Figure 1B). FDG-PET showed high metabolic activity with the maximum standardized uptake value (SUVmax) of 12.1 in a 2.5 cm solid mass adjacent to the cyst (Figure 1C). The timeline of follow-up evaluations and treatment for the thymic cyst and adjacent nodule is presented in Figure 1D.
PMC8794359_02
Gross and histological images. (A) The cross-sectional gross image showed a cyst (arrow) and an ill-defined solid nodule (arrowhead) adjacent to the cyst in the thymus. A red dotted-line square represented an area shown in B; (B) histological image of hematoxylin-eosin staining of the cyst and the adjoining nodule showed foam cell accumulation and cholesterol cleft granulation (yellow arrowheads). There was a rupture of the cyst wall (red arrow). There were thymic tissues around the granulation tissue (blue arrow). A blue dotted-line squares represented areas shown in C and D; (C) high magnification image (x40) showed a thymic tissue (upper) and a cholesterol cleft (lower). (D) high magnification image (x40) showed a rupture of the cyst wall through which the cyst and the nodule directly connected.
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A solid mass adjacent to the cyst consisted of cholesterol cleft granulation which directly connected to the thickened part of the cystic wall through a rupture of the wall (Figure 2).