Abdominal cancers include adrenocortical tumors, carcinomas of the stomach, cancer of the pancreas, colorectal carcinomas, carcinoid tumors, and gastrointestinal stromal tumors. The prognosis, diagnosis, classification, and treatment of these abdominal cancers are discussed below. It must be emphasized that these cancers are seen very infrequently in patients younger than 15 years, and most of the evidence is derived from case series. (Refer to the Renal Cell Carcinoma section in the PDQ summary on Wilms Tumor and Other Childhood Kidney Tumors for more information.)
Carcinoma of the Adrenal Cortex
Adrenocortical tumors encompass a spectrum of diseases with often seamless transition from benign (adenoma) to malignant (carcinoma) behavior. Their incidence in children is extremely low (only 0.2% of pediatric cancers). Adrenocortical tumors appear to follow a bimodal distribution, with peaks during the first and fourth decades.[2,3] In children, 25 new cases are expected to occur annually in the United States, for an estimated annual incidence of 0.2 to 0.3 cases per 1 million. Internationally, however, the incidence of adrenocortical tumors appear to vary substantially. The incidence of adrenocortical tumors is particularly high in southern Brazil, where it is approximately 10 to 15 times that observed in the United States.[5,6,7] Childhood adrenocortical tumors typically present during the first 5 years of life (median age, 3–4 years), although there is a second, smaller peak during adolescence.[8,9,10,11] Female gender is consistently predominant in most studies, with a female to male ratio of 1.6 to 1.
Predisposing genetic factors have been implicated in more than 50% of the cases in North America and Europe, and in 95% of the Brazilian cases. Germline TP53 mutations are almost always the predisposing factor. In the non-Brazilian cases, relatives of children with adrenocortical tumors often, although not invariably, have a high incidence of other non-adrenal cancers (Li-Fraumeni syndrome); germline mutations usually occur within the region coding for the TP53 DNA-binding domain (exons 5 to 8, primarily at highly conserved amino acid residues). In the Brazilian cases, in contrast, the patients' families do not exhibit a high incidence of cancer, and a single, unique mutation at codon 337 in exon 10 of the TP53 gene is consistently observed. Patients with Beckwith-Wiedemann and hemihypertrophy syndromes have a predisposition to cancer, and as many as 16% of their neoplasms are adrenocortical tumors. Hypomethylation of the KCNQ1OT1 gene has also been associated with the development of adrenocortical tumors in patients without the phenotypic features of Beckwith-Wiedemann syndrome. However, less than 1% of children with adrenocortical tumors have these syndromes. The distinctive genetic features of pediatric adrenocortical carcinoma have been reviewed.