Abstract
BackgroundPatients with 13q-syndrome are at risk of retinoblastoma when the RB1 gene, located in the chromosomal band 13q14.2, is deleted. This syndrome is frequently associated with congenital malformations and developmental delay, although these signs could be mild. Mosaic 13q-deletion patients have been previously reported in the literature; their phenotype is variable, and they may not be recognized.Case presentationRetinoblastoma diagnosed in a child with 13q-mosaicism confirmed in blood, oral mucosa, healthy retina and retinoblastoma. A second RB1 hit is present exclusively in the retinoblastoma sample (RB1 c.958C>T p.Arg320Ter). Other detected molecular events in retinoblastoma are 6p12.3pter gain and 6q25.3qter loss. Clinical examination is unremarkable except for clinodactyly of the right fifth finger.Discussion and conclusionsWe describe a case of mosaic 13q deletion syndrome affected by retinoblastoma. Molecular data obtained from the tumor analysis are similar to previous data available about this malignancy. High clinical suspicion is essential for an adequate diagnosis of mosaic cases.
Highlights
Patients with 13q-syndrome are at risk of retinoblastoma when the RB1 gene, located in the chromo‐ somal band 13q14.2, is deleted
We describe a case of mosaic 13q deletion syndrome affected by retinoblastoma
Because of the fact that 98% of retinoblastoma cases begin after a double RB1 hit, according to Knudson’s hypothesis [3], all these children are at a major risk of being affected
Summary
We described the case of a child with 13q-mosaicism affected by retinoblastoma. The unilateral presentation agrees with previous data available for 13q deletions larger than 1 Mb including MED4 and SUCLA2 [6]. Cytogenetic analysis has shown recurrent CNVs (copy number variation) among retinoblastoma tumors, which are mainly chromosomal gains at 1q, 2p, 6p, 13q and 19q and losses at 13q, 16q and 17p [15] These recurrent aberrations allow to establish as a possible hypothesis that genes located at these loci could be related to retinoblastoma progression [15], yet no conclusive data are available about this at the moment. A terminal 6q deletion may be present in ovarian cancer and neuroblastoma [17] and seems to be related to bad prognosis in neuroblastoma [17] The fact that this deletion could play a role in retinoblastoma development in the context of 13q-syndrome is unknown. The BRCA2 gene, located in 13q13.1, may be lost in some 13q-patients Heterozygous mutations in this gene predispose to breast and ovarian cancer syndrome in adulthood [21] and a complete deletion of this gene might predispose to these tumors as well.
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