TTF1 and neoplasm: Histological findings of the left pleural mass showed adenocarcinoma, thyroid follicle formation (Figure 5A), and immunohistochemistry demonstrated strong and diffuse positive staining for TTF‐1 (Figure 5B) and thyroglobulin (Figure 5C) in over 90% of tumour cells, leading to the diagnosis of pleural metastasis from papillary thyroid carcinoma.