Incidence

Germ cell tumors are uncommon in children and are presumed to originate from primordial germ cells. These tumors occur at varied primary sites, both gonadal and extragonadal, and manifest in a variety of different histologies. Germ cell tumors represent approximately 7% of all cases of cancer in children and in adolescents less than 20 years of age. They account for 2 to 4% of all cancers in children younger than 15 years of age and approximately 14% for those between 15 and 19 years of age.1,2 The incidence for males younger than 20 years of age is slightly higher than that for females (12 vs 11.1 per million).

Unlike in adults, the incidence of extragonadal tumors exceeds that of gonadal tumors in children less than 15 years of age. However, in the population aged 15 to 19 years, the testicles and ovaries are the most common sites of tumor origin. Several large pediatric series show that approximately 59% of these tumors originate in extragonadal sites and that 41% originate in the gonads.3

The incidence of germ cell tumors peaks at two distinct ages. The first peak occurs before 2 years of age, reflecting the high incidence of sacrococcygeal tumors.4,5 The incidence then declines to very low levels before increasing again between 8 and 12 years of age for females and between 11 and 14 years of age for males. This later peak represents an increase in the incidence of both testicular and ovarian tumors in older children and adolescents.

According to data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program, the incidence of germ cell tumors has increased from 3.4 per million between 1975 and 1979 to 5.1 per million between 1990 and 1995 for children less than 15 years of age. For infants and younger children, the increase resulted from higher rates of extragonadal tumors. However, this increase must be interpreted with caution since it may represent the improved recognition by pathol-ogists of malignant tissue foci in mature and immature sacrococcygeal teratomas.6,7 For adolescent males, the increase in incidence is attributed to central nervous system (CNS) and testicular germ cell tumors whereas for females, it is attributable to ovarian germ cell tumors.

The incidence of germ cell tumors is lower in black children (7 per million) when compared with white children (10.7 per million). This difference reflects the lower rate of gonadal germ cell tumors among black children than among white children (3.2 per million and 12.3 per million, respectively).

To understand more clearly the incidence patterns of germ cell tumors in children, one needs to recognize that the biologic behavior of these tumors in infancy and early childhood is significantly different from their biologic behavior in older children and adolescents.1,4,8 Table 22-1 describes the clinical behavior and biologic characteristics of pediatric germ cell tumors. In the pediatric population, approximately 56% of all germ cell tumors are mature teratomas, 11% have immature tissues with

Table 22-1. BIOLOGIC CHARACTERISTICS OF PEDIATRIC GERM CELL TUMORS

Site

Age Group

Histology

Symptoms

Characteristics

Extragonadal

Sacrococcygeal Infants, young children

Mediastinal

Intracranial

Other

Gonadal Ovary

Testicle

Adolescents, older children

Adolescents, older children

Infants, young children

Early teens, adolescents, young adults

Infants, adolescents, young adults

50-65% mature, 5-15% immature, 10-30% malignant

60% mature, 40% malignant

50-60% germinomas, 20-40% nongerminomas

50-60% mature, 20-30% immature, 10-20% malignant

50-65% mature, 5-10% immature, 15-30% malignant

15-20% mature, 80-85% malignant

Presence of mass, constipation, urinary symptoms, lower back pain, lower-extremity weakness/sensory disturbance

Cough, wheezing, shortness of breath, superior vena cava syndrome Visual disturbances, diabetes insipidus, hypopituitarism, Parinaud's syndrome

Presence of a mass, pain, abdominal distention

Abdominal pain (chronic, acute), abdominal mass, amenorrhea, vaginal bleeding

Nontender mass, pain with torsion, abdominal distention; precocious puberty

About 35% of all GCTs; more common in females. Degree of externally visible mass and intrapelvic extension varies, as well as frequency of malignant histology. Rate of malignant tumors is higher in older patients with larger intrapelvic component.

About 4% of all GCTs; more common in males; frequently associated with Klinefelter's syndrome

About 5% of all GCTs; more common in males; found most frequently in pineal and suprasellar region, rarely intraspinal.

About 10% of all GCTs. Sites are head and neck, abdominal wall, retroperitoneum, vagina

About 25% of all GCTs; unusual in children younger than 2 years: associated with gonadal dysgenesis

About 15% of all GCTs; associated with cryptorchidism and gonadal dysgenesis; may be associated with hydrocele

GCT = germ cell tumor.

or without mature elements, and 33% contain frankly malignant components.4'5'9

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