Fig. 7.30 Kernicterus.Severehyperbilirubinemiaintheneonatalperiod—forexample,secondarytoimmunehydrolysis—resultsindepositionofbili-rubinpigment(arrows) inthebrainparenchyma.Thisoccursbecausetheblood–brainbarrierislessdevelopedintheneonatalperiodthanitisinadulthood.Infantswhosurvivedeveloplong-termneurologicsequelae.
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Fetalhydropsreferstotheaccumulationofedemafluidinthefetusduringintrauterinegrowth.
Thedegreeoffluidaccumulationisvariable,fromgeneralizedhydropsfetalistolocalizedcystichygromas.
Themostcommoncausesoffetalhydropsarenonimmune(chromosomalabnormalities,cardiovasculardefects,andfetalanemia),whereasimmunehydropshasbecomelessfrequentasaresultofRhantibodyprophylaxis.
Erythroblastosisfetalis(circulatingimmatureerythroidprecursors)isacharacteristicfindingoffetalanemia-associatedhydrops.
Hemolysis-inducedhyperbilirubinemiacanresultinbilirubintoxicity(kernicterus)inthebasalgangliaandbrainstem,particularlyinprematureinfants.
Malignant neoplasms constitute the second most common cause of death in children between the ages of 4 and 14 years; only accidents exact a higher toll. Benign tumors are even more common than cancers.
It is sometimes difficult to segregate, on morphologic grounds, true tumors from tumorlike lesions in the infant and child. In this context, two special categories of tumor-like lesions should be recognized:
Heterotopia or choristoma refers to microscopically normal cells or tissues that are present in abnormal locations. Examples are a pancreatic tissue “rest” found in the wall of the stomach or small intestine and a small mass of adrenal cells found in the kidney, lungs, ovaries, or elsewhere. Heterotopic rests usually are of little clinical significance, but on the basis of their appearance they can be confused with neoplasms.
Hamartoma refers to an excessive but focal overgrowth of cells and tissues native to the organ in which it occurs. Although the cellular elements are mature and identical to those found in the remainder of the organ, they do not reproduce the normal architecture of the surrounding tissue. The line of demarcation between a hamartoma and a benign neoplasm frequently is tenuous and is variously interpreted. Hemangiomas, lymphangiomas, rhabdomyomas of the heart, and adenomas of the liver are considered by some researchers to be hamartomas and by others to be true neoplasms.
Virtually any neoplasm may be encountered in the pediatric age group, but three—hemangiomas, lymphangiomas, and teratomas—deserve special mention here.
Hemangiomas are the most common neoplasms of infancy. Both cavernous and capillary hemangiomas may be encountered (Chapter 10), although the latter often are more cellular than in adults and thus may appear deceptively worrisome. In children, most hemangiomas are located in the skin, particularly on the face and scalp, where they produce flat to elevated, irregular, red-blue masses; the flat, larger lesions are referred to as port-wine stains. Hemangiomas may enlarge as the child ages, but in many instances they spontaneously regress (
Fig. 7.31 ). The vast majority of superficial hemangiomas have no more than a cosmetic significance; rarely, they may be the manifestation of a hereditary disorder associated with disease within internal organs, such as the von Hippel-Lindau syndrome (Chapter 10). A subset of CNS cavernous hemangiomas can occur in the familial setting; affected families harbor mutations in one of three cerebral cavernous malformation (CCM) genes.