PMC5994738_01
(A, B) Computed tomography (CT) scan results, showing a large anterior mediastinal mass occupying most of the left hemithorax and compressing the adjacent structures.
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Computed tomography (CT) revealed the mass to be 112 mm x 191 mm x 184 mm in size, located in the left anterior mediastinum, with a primary consideration of a lipoma (Fig. 1).
(A) Left posterolateral thoracotomy was performed and the mass was glossy in appearance. (B, C) Completely resected, the mass measured approximately 112 mm x 191 mm x 184 mm in size and weighed 2141 g. (D) The pleural effusion was milky in appearance and sent for further examination.
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During surgery, a tumor weighing 2141 g (Fig. 2), with the pedicle originating from the upper thymus gland on the left side, was excised. Thoracentesis was performed and the fluid was milky in appearance, with suspended fat droplets (Fig. 2).
(A, B) Thymic hyperplasia: the thymic architecture is conserved, consisting of a corticomedullary differentiation and the presence of Hassall's corpuscles in the medulla (H&E stain, A x 20; B: x200). (C, D) The cells were diffusely positive for Ki67 and TdT, indicating that they are medullary thymic epithelial cells. (E-G) The cells were focally positive for CK19, CK5/6 and P63, suggesting that they were from thymic cortex. (H, I) The cells were negative for TG and TTF1, revealing that they weren't derived from thyroid gland. (Immunohistochemical tests, C-I: x100).
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Neither the presence of lymphoid cells with germinal centers nor evidence of malignancy was found (Fig. 3 A, B). On immunohistochemistry, the cells were diffusely positive for Ki67 and TdT and focally positive for CK19, CK5/6 and P63, while they were negative for TG and TTF1 (Fig. 3C-I).