Rapid frozen section in pediatric pathology.

Frozen section examination in pediatrics differs from that in adult practice in two ways. First, there is a high proportion of undifferentiated small-cell cancers in which it it difficult to make a definitive diagnosis without additional information. Second, there are special categories of congenital disorders where one is seeking not neoplasia but the presence, absence, or size of normal structures. In 520 pediatric frozen sections, there was a comparatively high incidence of deferred (5.6%) or inaccurate diagnoses (3.5%). However, as there were 99 small-cell cancers, it is perhaps surprising that the number was not greater. In the nervous system (208 cases), it was sometimes difficult to distinguish between malignant ependymoma and medulloblastoma. In other neoplasms, e.g., soft tissues and bone, the most important requirement was adequate clinical and radiological information. In Hirschsprung's disease (132 cases), ganglion cell detection was 100% accurate. In measuring the diameter of bile ducts in the porta hepatis during surgery for biliary atresia (18 cases), it was sometimes difficult to recognize ducts that had lost their epithelial lining.