Pathology of the Head and Neck

300 M.R. Canninga-Van DijkFig. 10.22. Uveal tract melanoma: detail of an epithelioid lesionconsisting of cells with a large amount of eosinophilic cytoplasmFig. 10.24. Retinoblastoma: a detached retina with small blueround cell proliferation10Fig. 10.23. Uveal tract melanoma: trans-scleral extension of thetumour10.4.5.2 LymphoidIntraocular lymphomas are not different from those occuringelsewhere in the body. Therefore, discussion oftheir features lies beyond the scope of this chapter.10.4.5.3 Retinoblastomaand PseudoretinoblastomaICD-O:9510/3Retinoblastoma is rare, but nevertheless the most commonintraocular malignant tumour of childhood, clinicallypresenting as a white mass behind the lens, resultingin the so-called cat’s eye reflex. Vision in the eye isimpaired, leading to strabismus. The tumour affectschildren younger than 5 years and can be unilateral orbilateral (30%). Retinoblastoma in adults is extremelyrare. Lesions with the typical clinical presentation butare of other kinds are called pseudoretinoblastoma. Theycan be other tumours (astrocytic hamartomas, haemangioblastomas),congenital malformations or inflammatoryconditions (especially solitary Toxocara granuloma).The accuracy of clinical diagnosis has been improvedby radiology, ultrasonography, CT scanning andnuclear magnetic resonance, and this has brought abouta considerable reduction in the number of such cases.The retinoblastoma gene, located on chromosome13q14 is a tumour-suppressor gene. Retinoblastoma canbe inherited (bilateral tumours in the first 2 years oflife) or sporadic (unilateral tumours in children aged 2–5 years). One-third of the patients with a sporadic retinoblastomashow a germline mutation and can transmitthe disease to their offspring. Compared with the generalpopulation, carriers of germline mutations in the retinoblastomagene, who survive retinoblastoma are at increasedrisk of early-onset second cancers, particularlysarcomas and brain tumours. External beam radiotherapyhas been a standard treatment for medium andlarge, or vision-threatening, intraocular retinoblastoma,but it markedly increases the risk of cosmetic deformitiesand secondary cancer in children with germline mutations.For that reason primary systemic chemotherapycalled “chemoreduction” has been employed to avoid radiotherapyand enucleation. The cure rate of retinoblastomais more than 90% in specialised centres.Retinoblastomas are tumours originating from pluripotentgerminal retinoblasts; the tumour can grow endophytically(growing into the vitreous), exophytically(growing into the subretinal space, leading to retinal detachment)or diffusely (a rare pattern with widespread