[RETINOBLASTOMA]. Retinoblastoma is the most common childhood intraocular neoplasm usually seen between 1-2 years of age. It can occur in a hereditary form or non-hereditary sporadic form. In both cases, however, patients have inactivating mutations of the retinoblastoma tumor suppressor gene on chromosome 13q14. The tumor arises from undifferentiated neuroectodermal cells that are the precursors of retinal neuroepithelium. This large endophytic tumor (arrow on the right) detaches the retinal epithelium (thin long arrow facing down). Note the proximity of the tumor origin with the retinal epithelium. The optic nerve is shown on the left (arrowhead).
[RETINOBLASTOMA]. This large tumor (arrow) is arising at about the root of the optic nerve (long arrow). Note the partially-preserved retinal epithelium on the left (curved arrow). However, the epithelium is detached and distorted by tumor growth. Sporadic tumors are usually unilateral whereas hereditary tumors are bilateral in over 90% of the cases. Hereditary retinoblastomas are often multifocal in the same eye and may be minute.
[RETINOBLASTOMA]. The tumor is composed of small undifferentiated cells that also form rosettes. Note the presence of multiple foci of necrosis. Calcifications are often present and can be detected on plain radiographs of the orbit and serve as an important diagnostic tool.
[RETINOBLASTOMA]. Microscopically, true rosette formation is seen in most tumors but by no means is a diagnostic criterion. Note the presence of apoptotic cells in between viable cells. The rosettes called “Flexner-Wintersteiner” rosettes are a sign of neuroectodermal differentiation.
[RETINOBLASTOMA]. The tumor cells are primitive undifferentiated cells with scant cytoplasm and round to oval nuclei showing finely granular chromatin and absence of nucleoli. This morphologic appearance is very similar to other undifferentiated neuroectodermal tumors such as medulloblastoma. Note the presence of apoptotic cell nuclei (arrowheads).
[RETINOBLASTOMA]. A true Flexner-Wintersteiner rosette is composed of oval tumor cells in a circular arrangement with polarization of cytoplasm toward the central lumen of the rosette and peripherally arranged nuclei. Note the absence of any blood vessels in the central lumen as opposed to papillary formations in certain other tumors.
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