An 18-month-old child is brought in because the mother noticed a white pupillary reflex in the right eye on photographs. Examination shows leukocoria and strabismus. CT scan reveals a calcified intraocular mass without extension beyond the globe. Mutation in which gene is most likely implicated?

• A RB1 ✓
• B APC
• C WT1
• D NF2

Explanation

Leukocoria in a toddler with a calcified intraocular mass is retinoblastoma, the commonest intraocular malignancy of childhood. It arises from biallelic inactivation of the RB1 tumor suppressor gene on chromosome 13q14, the prototype of Knudson's two-hit hypothesis. Germline RB1 mutations produce bilateral multifocal disease and predispose to osteosarcoma later in life. WT1 relates to Wilms tumor, APC to familial polyposis, and NF2 to vestibular schwannomas. Calcification within the mass is the classic imaging clue here.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.