CSF cytology--the ongoing dilemma to distinguish neoplastic and inflammatory lymphocytes.

To evaluate different morphological criteria for the distinction between inflammatory and neoplastic lymphocytes in the cerebrospinal fluid (CSF). Forty-two cytospin preparations of CSF from patients with confirmed CSF involvement by aggressive B-cell lymphoma or acute leukemia were compared with 26 samples of inflammatory diseases. CSF cytology was analyzed morphologically for preselected parameters of cell, cytoplasm and nucleic appearance, and the presence of mitoses or apoptoses. None of the evaluated parameters sharply discerns neoplastic and inflammatory changes. However, neoplastic cells were significantly larger. Moreover, irregular shape and pointed borders of the cytoplasm, and deep notches in the nucleus were significantly more frequent in neoplastic than in inflammatory lymphocytes. No single parameter is sufficient to detect neoplastic lymphocytes. Considering a combination of cell size and irregular shape of cell and nucleus, however, may improve the diagnostic accuracy of CSF dissemination by aggressive hematological malignancies.