Pathology- Retinoblastoma
A tumor suppressor gene called RB found on chromosome 13 is deleted in both alleles, resulting in a tumor originating from neuroepithelial cells in the retina. Can be hereditary or random. The familial form is inherited as an autosomal dominant characteristic, requiring homozygosity for disease manifestation. Over 90% of those who are heterozygous carriers ultimately get the condition. The retina consists of circular cells with darkly stained nuclei and little cytoplasm organized in Flexner-Wintersteiner rosettes (cuboidal cells surrounding a central lumen). Can spread to the brain, spinal cord, bone, or lymph nodes. Medical Typically seen in young children (familial form) who display reduced visual acuity, eye discomfort, strabismus, intraocular mass on funduscopic examination, and white cat's eye pupillary reflex. Individuals with familial disease are prone to getting retinoblastoma in both eyes and have a heightened susceptibility to other malignancies such as osteosarcoma. Surgical excision of tumor or eye if required, followed by radiation therapy. A tumor becomes lethal after it has metastasized beyond the eye. Notes Knudson's two-hit hypothesis prototype: Two mutations are necessary for the disease to occur. Deletion can be either hereditary (familial) or sporadic. The second mutation arises sporadically in both familial and sporadic instances.
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