Occurrence of colon tumors in a 16-year-old Japanese boy after hematopoietic stem cell transplantation for Diamond Blackfan anemia at age of 4: a case report.

Diamond Blackfan anemia (DBA) is a congenital pure red cell aplasia mainly caused by a mutation in ribosomal protein genes. One of the proposed mechanisms for red cell aplasia in DBA is apoptosis caused by constitutive activation of tumor suppressor TP53 protein following defective ribosome biogenesis. Because of this close relationship between ribosome biogenesis and TP53 activation, patients with DBA are considered to be cancer-prone. The association between bone marrow failure and tumor susceptibility in DBA appears paradoxical. Also, the detailed information is lacking on malignancy occurring in patients with DBA. Here, we report a case of a 16-year-old Japanese boy suffering from multiple colon tumors during the follow-up after hematopoietic stem cell transplantation for DBA at the age of 4. Well differentiated tubular adenocarcinoma was detected at the rectum 12 years after the transplantation, followed by multiple tubular adenomas of low to high grade throughout the colon. Endoscopic submucosal dissection was performed for these tumors and the lesions were completely resected. These tumors did not show diffuse and strong TP53 positivity by immunohistochemistry, suggesting that TP53 mutation was not involved in the tumorigenesis as observed in conventional colorectal cancers. Microsatellite instability test and immunohistochemical examination of β-catenin and MLH1 proteins of these tumors showed that WNT signaling or microsatellite instability was less likely to be involved in the present tumors as observed in conventional left-sided or right-sided colon cancers, respectively. To our knowledge, this is the first case report of colon tumors associated with DBA.