The Cytopathology Section provides complete diagnostic service in exfoliative cytology and fine needle aspiration cytology. The section also routinely applies immunocytochemistry techniques to confirm and/or enhance cytological diagnostic accuracy. In addition, the section collaborates in various clinical research projects utilizing routine microscopy as well as special staining techniques, immunocytochemistry, and flow cytometry. The fine needle aspiration service is designed to afford maximal flexibility for clinicians and patients. Clinicians may request that: 1) a pathologist perform the aspiration; 2) a pathologist instruct the clinician in aspiration technique; 3) a cytotechnologist assist the clinician in handling the specimen; 14) aspirations of deep lesions be performed by the radiologist with the assistance of a cytotechnologist to evaluate adequacy of the specimen. An example of one collaborative clinical research project involves clinical trials currently being conducted to study the use of the monoclonal antibody 454A12MAB-RICIN A chain conjugate given intrathecally for refractory carcinomatous meningitis. Our collaborative effort in this project involves the cytomorphologic evaluation of cerebrospinal fluid (CSF) specimens in order to: 1) document the presence of malignancy in the CSF prior to initiation of intrathecal immunotoxin therapy; 2) establish the baseline CSF tumor burden prior to therapy; and 3) monitor the cytologic response quantitatively throughout the post-therapy period. Another collaborative project with critical care medicine is comparing the diagnostic sensitivities of bronchoalveolar lavage, sputum, transbronchial biopsy, and various culture and immunocytochemical techniques in the detection of CMV in HIV positive patients. We are also performing in situ hybridization studies on cytopathologic material, probing for CMV viral DNA.