Clinically, retinoblastoma may be described as endophytic or exophytic. What do you understand by these terms?

Answer
Exophytic retinoblastoma refers to tumour growth in the subretinal
space giving rise to retinal detachment. The tumour may invade the 
Bruch's membrane to enter the choroid and spread to the blood vessels,
ciliary nerve and vessels.
Endophytic tumour refers to tumour growth into the vitreous space 
and the tumour appears as one or more tumour masses on the retina 
surface. Extensive cases may give the appearance of endophthalmitis with pseudo-hypopyon.
However, both exophytic and endophytic patterns may co-exist in the same tumour.
 
 

Patient 1

Patient 2

The above are two clinical pictures of retinoblastoma. Which is endophytic and which is exophytic retinoblastoma?

Answer
Patient 1 has endophytic retinoblastoma. In endophytic retinoblastoma,
the details of the retinal structures may be obscured due to tumour size
or vitreous seedings.
Patient 2 has exophytic retinoblastoma. Note the retinal detachment and the easy visibility of the retinal vessels.
 
 

The above picture is an enucleated specimen of retinoblastoma.
What are the blue areas in this H&E stain?

Answer
They are areas of necrosis. Retinoblastomas often overgrow
their blood supply causing areas of necrosis. The tumour cells 
are high in DNAs and when they die, the DNAs leak out and 
give rise to basophilic (blue) staining.

What factors are important in the prognosis of retinoblastoma?

Answer
Location of the tumour. If there is extraocular extension or optic nerve involvement, the 5 year survival is low. 
Other adverse factors include: large tumour size, presence of 
bilateral tumours (this indicates the risk of second tumour) and
older age at diagnosis (indicates the tumour has been present much longer)

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