Anatomic Pathology: Pediatric and Placental Pathology

1112) Which of the following is TRUE about this intraocular tumor?

• Retinoblastoma and the Rb gene were the basis for Knudson’s two-hit hypothesis. Rb is a tumor suppressor gene, therefore both copies need to be inactivated in order to cause cancer. The first “hit” (mutated gene) can be inherited/germline or sporadic, the second “hit” is sporadic. This is why familial retinoblastoma occurs at a younger age.

• Most retinoblastomas (90% to 95%) are sporadic, even in those patients with germline Rb mutations. The germline mutation in these patients is de novo.

• Exophytic growth is in the subretinal space, and is associated with retinal detachment. Endophytic growth occurs when the tumor breaks through the retinal limiting membrane, and is associated with vitreous seeding. Both will make an intraocular mass.

• Homer-Wright rosettes are pseudorosettes, they don’t have a central lumen. Flexner-Wintersteiner rosettes do have a central lumen. Both can be seen in retinoblastoma, but Flexner-Wintersteiner rosettes are classic. Fleurettes may also be seen in very well-differentiated tumors.

• Extensive necrosis and calcifications are common.

Chawla B, Sharma S, Sen S, et al: Correlation between clinical features, magnetic resonance imaging, and histopathologic findings in retinoblastoma: a prospective study. Ophthalmology 2012;119(4):850-856.

de Oliveira Reis AH, de Carvalho IN, de Sousa Damasceno PB, et al: Influence of MDM2 and MDM4 on development and survival in hereditary retinoblastoma. Pediatr Blood Cancer 2012;59(1):39-43.

Dommering CJ, Marees T, van der Hout AH, et al: RB1 mutations and second primary malignancies after hereditary retinoblastoma. Fam Cancer 2012;11(2):225-233.

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