S45F mutation may offer identifiable risk factor in recurrent pediatric aggressive fibromatosis

In the case of aggressive fibromatosis, the good news is that it is a slow-growing benign tumor. The bad news is that this abdominal tumor often recurs after surgical removal. This is particularly true among children. While headway has been made in isolating causes of this recurrence in adults, it is less clear in children.

The current issue of the journal Pediatric and Developmental Pathology includes a study of the role of the protein β-catenin in pediatric aggressive fibromatosis. Researchers analyzed the expression and mutation status of β-catenin in this tumor.

Although it is rare, with only two to four cases per million people, aggressive fibromatosis shows infiltrative growth. The tumor is benign, but it can harm other structures within the body and cause organ dysfunction, so it is often removed. However, pediatric aggressive fibromatosis has a recurrence rate of 75 percent, higher than that of adults.

Through immunohistochemistry, the current study analyzed biopsy samples from 32 patients, 21 of whom were experiencing recurrent cases of the tumor. All patients were between the ages of 3 and 15. The study found that abnormal expression of β-catenin appears to be frequent in pediatric aggressive fibromatosis.

Furthermore, somatic point mutations in β-catenin exon 3 were identified. The mutation was found in 78 percent of the cases: 19 of the 21 recurrent cases, and 6 of the 11 primary-onset cases. All the mutations in the recurrent cases were located in codon 45 (S45F). With the exception of one patient, all the primary case mutations were found in a different location—codon 41.

This mutation was identified more frequently in this study of pediatric cases than in previous studies of adults. The higher frequency may be the underlying factor in the higher rate of pediatric recurrence. The authors conclude that the S45F mutation may offer an identifiable risk factor in recurrent pediatric cases of aggressive fibromatosis.