Immunophenotyping of cytologic specimens by flow cytometry

Immunophenotyping by flow cytometry is well established as an ancillary technique in the diagnosis of hematopoietic neoplasms. However, flow cytometry is rarely performed on cytologic specimens because most cytologists are more comfortable with direct microscopy and believe that there is inadequate cellularity for analysis. Paradoxically, cytologic material is usually cell suspensions making it ideal for flow cytometry. In order to evaluate the usefulness of immunophenotyping cytologic specimens by flow cytometry, we retrospectively reviewed all cytologic specimens submitted to our flow cytometry unit from 1988 to 1991. Thirty-one cerebrospinal fluid specimens were analyzed. There were inadequate cells for analysis in 15 cases. Five showed a monoclonal proliferation; 11 were nondiagnostic. A range (r) of one to six cell surface markers were performed. Thirty-two body cavity fluids were analyzed: 7 peritoneal, 19 pleural, 2 pericardial, and 4 bronchoalveolar lavage. There were cells to analyze in all cases. Seven had a monoclonal proliferation; 25 were nondiagnostic (r = 4-21 markers performed). One hundred eighteen fine needle aspirates (FNA) were reviewed; 58 FNA were radiologically guided, 60 were superficial lesions. There were inadequate cells for analysis in two cases. Sixty-one demonstrated a monoclonal proliferation; 55 were nondiagnostic (r = 1-22 markers performed). We conclude that immunophenotyping by flow cytometry is of limited value for cerebrospinal fluid analysis and that knowledge of previous immunophenotyping studies is essential for correct analysis; analysis of body cavity fluids is easily performed but less often demonstrates a monoclonal proliferation. Immunophenotyping by flow cytometry is a valuable adjunctive technique for FNA and yields adequate cells for analysis.