PMC9082352_01
Lung (A) and mediastinal window (B) of axial CT images show an irregular mass (about 5.1 x 3.5 cm) in the right anterior upper mediastinum, with inhomogeneous enhancement on contrast-enhanced CT (C).
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CYFRA21-1, CA15-3, CA19-9, and CA12-5). Chest CT showed an irregular mass (51 mm x 35 mm) in the anterior mediastinum, with inhomogeneous enhancement on contrast-enhanced CT ( Figure 1 ).
Histopathological analysis revealed type AB thymoma composed of a lymphocyte-poor area and lymphocyte-rich area at low magnification (A, B). Clusters of mononuclear cells and eosinophils (C) were surrounded by lesions of thymoma (H&E, magnification x400), and immunohistochemical tests showed these clusters were positive for S100 (D), CD1a (E), and Langerin (F), identifying the diagnosis of Langerhans cell histiocytosis in the thymus.
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Small nodules of mononuclear cells and eosinophils were surrounded by lesions of thymoma, and immunohistochemical tests showed that these nodules were positive for S100, CD1a, and Langerin ( Figure 2 ).
18F-FDG PET/CT was performed on this patient to evaluate the extent of the Langerhans cell histiocytosis (LCH). The maximum intensity projection (MIP) revealed increased 18F-FDG uptake in the chest, left femur, and right thigh regions (A). Surgery-related changes of the sternum on the mediastinal window of axial CT (B) were shown with diffusely high 18F-FDG uptake and SUVmax as 4.08 on axial PET/CT fusion (C) and PET images (D). An 18F-FDG-avid lesion in the right atrial appendage was found with SUVmax as 7.08 on axial PET/CT fusion (F) and PET images (G), and no specific abnormal density was found in the corresponding region on the mediastinal window of axial CT image (E). A round mass (about 3.7 x 3.1 cm) in the right upper thigh on the soft tissue window of axial CT (H) was revealed with SUVmax as 3.20 on axial PET/CT fusion (I) and PET images (J). A hypermetabolic lesion in the left upper femur was found with SUVmax as 3.98 on axial PET/CT fusion (L) and PET images (M); bone marrow density was slightly increased (K).
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This patient also received radiotherapy after thymectomy (GTV5500cGy/25f, CTV5000cGy/25f). 18F-FDG-PET/CT was performed ( Figure 3 ) and showed abnormal hypermetabolic regions in the chest, left femur, and right thigh, with the following maximum standardized uptake value (SUVmax): surgery-related changes of the sternum, 4.08; right atrial appendage, 7.08; a round mass with a size of 37 mm x 31 mm at the right upper thigh, 3.20; and left upper femur, 3.98.