Unusual Cancers of Childhood Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Abdominal Cancers
Most tumors in the pediatric age group are poorly differentiated mucin-producing carcinomas and many are of the signet ring cell type,[71,74,78] whereas only about 15% of adult lesions are of this histology. The tumors of younger patients with this histologic variant may be less responsive to chemotherapy. In the adolescent and young adult population, colorectal cancers have a higher incidence of mucinous histology, signet ring cells, microsatellite instability, and mutations in the mismatch repair genes. These tumors arise from the surface of the bowel, usually at the site of an adenomatous polyp. The tumor may extend into the muscle layer surrounding the bowel, or the tumor may perforate the bowel entirely and seed through the spaces around the bowel, including intra-abdominal fat, lymph nodes, liver, ovaries, and the surface of other loops of bowel. A high incidence of metastasis involving the pelvis, ovaries, or both may be present in girls. Colorectal cancers in younger patients have a high incidence of microsatellite instability, and noninherited sporadic tumors in younger patients often lack KRAS mutations and other cytogenetic anomalies seen in older patients.
Genetic syndromes associated with colorectal cancer
About 20% to 30% of adult patients with colorectal cancer have a significant history of familial cancer; of these, about 5% have a well-defined genetic syndrome. The incidence of these syndromes in children has not been well defined. In one review, 16% of patients younger than 40 years had a predisposing factor for the development of colorectal cancer. A later study documented immunohistochemical evidence of mismatch repair deficiency in 31% of colorectal carcinoma samples in patients aged 30 years or younger. The most common genetic syndromes associated with the development of colorectal cancer are shown in Tables 3 and 4.
Table 3. Common Genetic Syndromes Associated With Adenomatous Polyposis
|Syndrome||Gene||Gene Function||Hereditary Pattern|
|Attenuated familial adenomatous polyposis||APC(5' mutations),AXIN2||Tumor suppressor||Dominant|
|Familial adenomatous polyposis (Gardner syndrome)||APC||Tumor suppressor||Dominant|
|Lynch syndrome (hereditary nonpolyposis colorectal cancer)||MSH2, MLH1, MSH6, PMS2, EPCAM||Repair/stability||Dominant|
|Li-Fraumeni syndrome||TP53(p53)||Tumor suppressor||Dominant|
|Turcot syndrome||APC ||Tumor suppressor||Dominant|