Figure 2. A pleural fluid sample. (A) A cluster of atypical lymphocytes. The cells have distinct nuclear bodies and a high nucleus-to-cytoplasm ratio. From these cells originates a net of filaments (filopodia-like filaments) that reach and trap surrounding cells (scale bar=50 µm). (B) A nanotube-like filament connects 2 atypical lymphocytes (arrow). Small particles of intensely-stained material are present in the cytoplasm as well as at the periphery of the nucleus and close to the cell membrane (scale bar=5 µm). (C) Densely-stained material similar to nuclear chromatin (white asterisk) is seen in the cytoplasm of atypical lymphocytes. The material gives rise to 2 thin tubes containing small particles of condensed material (short arrows), which probably were created when the main mass fragmented (scale bar=5 µm). (D, E) Unusually long, large-caliber cylindrical fibers (white arrows), many with truncated ends (asterisk in D), are seen in the pleural fluid. The black arrow points to the filopodia-like filaments (scale bar=10 µm).