The spectrum of orbital lesions occurring in childhood is wide, including a variety of both benign and malignant disorders. Although physical examination and fundoscopy may aid in establishing the diagnosis of retro-ocular lesions, imaging remains a critical step in the evaluation of the pediatric orbit. Ultrasonography, CT, and MR imaging are the primary modalities for the evaluation of the diseased orbit, and careful observation of the characteristic radiological features usually leads to correct diagnosis; however, some of the lesions look very similar and are difficult to differentiate from each other. The purpose of this article is to review the common and unusual entities that may involve the pediatric orbit, to describe the radiological features, and to evaluate the efficacy of US, CT, and MRI in the diagnosis and management of these conditions.
Mutation analysis of retinoblastoma is considered important for genetic counseling purposes, as well as for understanding the molecular mechanisms leading to tumors with different degrees of penetrance or expressivity. In the course of an analysis of 43 hereditary retinoblastoma Spanish patients and kindred, using direct PCR sequencing, we have observed 29 mutations; most of them (62%) have not been reported previously. Of the mutations, 69% correspond to nonsense mutations (mainly CpG transitions) and frameshifts, with the expected outcome of a truncated Rb protein that lacks the functional pocket domains and tail. The remainder corresponds to splicing mutations, most of them (62%) targeted to invariant nucleotides, with the predicted consequence of out of frame exon skipping. Two of the splicing mutations in our study were found associated to families with a low-penetrance phenotype. Additionally, most of the mutations affecting splice junctions corresponded to retinoblastoma cases of either sporadic or hereditary nature with delayed onset (32 months on average). In contrast, most of the nonsense and frameshift mutations are associated with an early age at diagnosis (8.7 months on average). These differences are discussed in the context of the relationships between genotype and low expressivity phenotype. The differences in the spectrum of RB1 mutations found in this and other European surveys are also discussed in the context of alternate DNA methylation and mismatch repair phenotypes.
Peripheral primitive neuroectodermal tumours (pPNETs) are a group of soft-tissue tumours of neuroepithelial origin that arise outside the central and sympathetic nervous system. Orbital location is infrequent, and to the best of the authors' knowledge only 16 cases have been reported in the literature. With this article, the authors report the demographics and clinical characteristics, diagnostic features, differential diagnosis, prognosis and therapeutic options of primary orbital peripheral primitive neuroectodermal tumour, based on their patients and on the cases reported in the literature to date. A differential diagnosis should be made with other small round cell tumours; immunohistochemical and ultrastructural techniques are essential for this purpose. Although bone invasion and extraorbital extension are possible, systemic metastases are uncommon in the cases of orbital pPNETs. Surgery has been the initial treatment in most cases; chemotherapy with or without radiotherapy is considered the best additional treatment. The orbital pPNET could be less aggressive than other forms of pPNETs, since most of the patients reported were alive after the follow-up period (at least 6 months).
Ultrasonography (US) is a rapid, accurate, noninvasive method of evaluating ocular and orbital disease. A wide spectrum of pediatric ocular and Ilew (.lata tbout the lesions seen by tile ophthalmologist. US is a usefui adjunct to ciinical evaluation tiiii ophthalmologic investigation because of its simplicity, rapidity, and Ilollilivasiveliess. Index ternis: i;yc. abnor,i,alitics. 22i. I i #{149} distas.'s. 22i.8(). injurks. 22i to. I' c. ncopla .ni .. .!2i.3() #{149} ()rl it. c 22.3 I 9 #{149} ()rhit, ifltLtI1 fl'I LtiOfl. 22.3 19 #{149} ()rhit, I1C()pIaSIuS.
Linkage analysis at the retinoblastoma locus (RB1) is essential for identifying individuals at risk and to offer adequate genetic counseling in familial retinoblastoma. It can also be used to detect large deletions involving RB1, which accounts for 15% of the genetic alterations in hereditary retinoblastoma. These studies are usually carried out with lengthy Southern blot analyses of relatively uninformative restriction fragment length polymorphisms. The authors report an alternative, reliable protocol for genotyping the RB1 locus using two pairs of highly informative intragenic and flanking microsatellites linked closely to the RB1 gene, and analysis of the fluorescent-labeled polymerase chain reaction products with automatic sizing technology. This methodology has successfully identified high risk carriers in five of the five pedigrees of familial retinoblastoma studied. In addition, gross deletions affecting the RB1 gene were identified in two of 12 sporadic bilateral retinoblastomas, and loss of heterozygosity at the RB1 locus has been detected in one of three osteosarcomas using the same experimental protocol. The described protocol is simpler and faster than conventional Southern blot methodologies and can identify a larger number of informative cases.
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