Touch preparations in the rapid intraoperative diagnosis of central nervous system lesions. A comparison with frozen sections and paraffin-embedded sections.

Cytologic preparations provide a rapid, simple method for intraoperative diagnosis of central nervous system (CNS) lesions. Details of cellular morphology are defined sharply, avoiding artifacts often introduced by the frozen section technique. In 100 neurosurgical biopsies performed between 1984 and 1986, touch preparations and cryostat (frozen) sections were made at the time of surgery for preliminary intraoperative diagnosis. To assess the accuracy of each of the diagnostic methods used independently, slides obtained with each of the two techniques were later reviewed retrospectively with appropriate clinical and radiological data, but without knowledge of the final neuropathological diagnoses. When compared with the final diagnoses, intraoperative diagnoses were confirmed in 95 cases. The diagnoses based on cytologic and frozen section techniques were compared with the final diagnoses based on paraffin sections. Touch preparation diagnosis was confirmed by paraffin sections in 76 cases; in 18 additional cases a clinically useful, but nonspecific diagnosis (benign versus malignant, glial versus nonglial) was established by touch preparation. In five cases with firm or rubbery tumors, insufficient cells were imprinted for reliable evaluation, and no definitive diagnoses could be made. Specific cryostat diagnoses were confirmed by paraffin sections in 88 cases; nonspecific diagnoses were made in 11 cases. A single incorrect diagnosis was obtained with each technique. When the two techniques were used together, a specific and accurate diagnosis was achieved in 95 cases. Touch preparations were superior to frozen sections for evaluating soft or highly cellular tumors and for preliminary diagnosis from a minute surgical specimen (i.e., stereotactic biopsy).(ABSTRACT TRUNCATED AT 250 WORDS)