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Special Feature
March 2000

Picture of the Month

Author Affiliations


Arch Pediatr Adolesc Med. 2000;154(3):310. doi:

Figure 1. A huge sacrococcygeal teratoma is attached to the infant's lower back. The cephalic portion of the tumor is necrotic.

Sacrococcygeal teratomas, although rare, are the most frequently recognized neoplasm in fetuses,1 with an incidence of approximately 1 in 35,000 to 40,000 live births.1 More common in female than male infants (4:12), a familial predisposition is present in some cases.3 The incidence of twins in the immediate family varies from 14% to 50%.

Teratomas are congenital tumors composed of tissues derived from all 3 embryonic germinal layers. Postsacral tumors are thought to arise from multipotential embryonic cells that occur in greatest concentration in the area of the primitive knot (Hensen node) and presacral tumors from incomplete migration of germ cells from the yolk sac to the urogenital ridge.3 The female gonads of the fetus terminate their differentiation at 10 weeks' gestation in contrast to 7 weeks' for the male. The multipotential cells, therefore, remain longer in the female gonads and are more prone to disturbances, which may account for the higher incidence of sacrococcygeal teratomas in females.4 Sacrococcygeal teratomas may be the result of twinning or abortive attempts at twinning, which may account for the higher incidence in monozygotic twins.