Pathology Cheat Sheet
Two Hits, One Retina
Retinoblastoma for NEET-PG: RB1 gene 13q14, two-hit hypothesis, hereditary vs sporadic, leukocoria, Flexner-Wintersteiner rosettes, and osteosarcoma risk.
MedNext Academy | 3 min read
Two Hits, One Retina
Retinoblastoma for NEET-PG: RB1 gene 13q14, two-hit hypothesis, hereditary vs sporadic, leukocoria, Flexner-Wintersteiner rosettes, and osteosarcoma risk.
The genetics, pathology and presentation of retinoblastoma, the prototype two-hit tumour of childhood.
High-yield lines
- Retinoblastoma is the most common intraocular malignancy of childhood.
- Retinoblastoma is caused by biallelic inactivation of the RB1 tumour suppressor gene on chromosome 13q14.
- The Knudson two-hit hypothesis explains hereditary and sporadic forms of retinoblastoma.
- Hereditary retinoblastoma has one germline mutation and is often bilateral and multifocal.
- Sporadic retinoblastoma requires two somatic hits and is usually unilateral.
- Retinoblastoma classically presents with leukocoria, a white pupillary reflex.
- Strabismus is another common presenting feature of retinoblastoma.
- Retinoblastoma shows small round blue cells forming Flexner-Wintersteiner rosettes.
- Flexner-Wintersteiner rosettes have a central lumen indicating photoreceptor differentiation.
- Areas of necrosis with dystrophic calcification are common in retinoblastoma.
- Hereditary retinoblastoma carries an increased risk of osteosarcoma later in life.
- The RB protein normally controls the G1 to S checkpoint by binding E2F.
Mapped competency codes
- PA36.1
Continue into the full chapter
This summary maps to PA36-eye.
Frequently Asked Questions
What gene is inactivated in retinoblastoma?
The RB1 tumour suppressor gene on chromosome 13q14, which requires inactivation of both alleles per the Knudson two-hit hypothesis.
How do hereditary and sporadic retinoblastoma differ?
Hereditary retinoblastoma has a germline first hit and is often bilateral and multifocal, while sporadic retinoblastoma requires two somatic hits and is usually unilateral.
What is the classic presenting sign of retinoblastoma?
Leukocoria, a white pupillary reflex, often accompanied by strabismus in an affected child.
What are Flexner-Wintersteiner rosettes?
Rosettes with a central lumen formed by tumour cells with photoreceptor differentiation, characteristic of retinoblastoma.
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