Cytology of fluids from pleural, peritoneal and pericardial cavities in children. A comprehensive survey.

We reviewed all cytologic specimens of pleural, peritoneal and pericardial fluids examined in our laboratory from patients aged 0-17 years during a 12-year period. A total of 103 specimens were studied: 45 pleural, 54 peritoneal and 4 pericardial. Twenty-two of the 103 specimens were peritoneal washes. Eleven of the 81 (14%) serous effusion specimens contained tumor cells: 8 lymphomas, 1 leukemia, 1 abdominal desmoplastic small round cell tumor and 1 Wilms' tumor. Two false-positive diagnoses were made in patients presenting with ascites with an unknown case. Both cases were complicated by the presence of atypical mononuclear cells and illustrate a potential pitfall in the evaluation of pediatric serous effusions. We conclude: (1) Almost all pediatric effusions are benign. (2) Malignant pediatric effusions are usually caused by neoplasms of the small cell type, mostly lymphoreticular. (3) The major diagnostic difficulty in interpreting pediatric effusion cytology is in distinguishing neoplasms of the small cell type from mononuclear inflammatory cells. (4) The usefulness of peritoneal washings in pediatric patients is similar to that in adults.