Fig. 1

False-positive cases in pleural effusion specimens. Case 1: The cytological diagnosis was ‘SFM (IVa)’ (A, HE, × 400), while the histological diagnosis was granulomatous lesions (B, HE, × 200). We think that the epithelioid cells in the granulomatous lesions (bottom right of the Figure B) may have been mistaken for SFM. Case 2: The cytological diagnosis was ‘SFM (IVa)’ (C, HE, × 100), while the clinical diagnosis was ‘tuberculosis’. The patient had a history of abdominal lymphoma. A few weeks after the cytological diagnosis, he was clinically diagnosed with thoracic tuberculosis, and the pleural fluid disappeared after anti-tuberculosis treatment. The history of lymphoma may have led to our incorrect diagnosis. Case 3: The cytological diagnosis was ‘SFM (IVa)’ (D, Papanicolaou stain, × 400), while the clinical diagnosis was ‘chylothorax’. The misdiagnosed cells may be reactive mesothelial cells caused by chylothorax