Electron microscopy of fine-needle aspiration biopsies of the mediastinum.

Twenty cases of fine-needle aspiration (FNA) biopsy of mediastinal tumors with ultrastructural studies of the aspirated material were reviewed. The cases were classified according to the cytologic and ultrastructural diagnosis. A specimen insufficient for ultrastructural study was obtained in five cases (25%). Refinement of the cytologic diagnosis was made in three cases (15%) and good correlation between the initial cytologic impression and the ultrastructural studies was seen in the remaining cases (60%). Comparison of different sites of FNA biopsy revealed a higher rate of ultrastructural examination in the cases involving the mediastinum. Illustrative cases of the use of electron microscopy in FNA biopsies of mediastinal tumors are presented.