In this lecture, we will quickly review retinoblastoma in childhood; tumor of the eye.
Here is the characteristics of retinoblastoma.
It happens in one in 20,000 live births
and thus there's about just over 300 cases every year in the United States and Canada.
So it's not that common, but it's a unique condition, so we'll discuss it.
Patients may have unilateral or bilateral retinoblastoma.
The unilateral disease is typically a spontaneous mutation in the Rb1 gene.
This is 70% of cases, and it typically presents between the age of two and five.
On the flipside, we can see bilateral disease.
This is a result of having inherited a mutation in the Rb1 gene and just getting a second hit.
This is 30% of cases and this presents in children under of year of age so they present a little bit earlier.
This is one of the typical, small blue round cell tumors,
it's intraocular and it presents typically in infancy in patients who've inherited the disease.
It's associated with a genetic mutation of Rb1 or the retinoblastoma gene.
Rb1 is an important oncongenic tumor suppressor gene found on the 13th chromosome at 13q14.
Basically, a mutation in this gene causes cellular proliferation and cell cycle dysregulation,
resulting in a clonal population of cells that can form tumors typically in the eye.
And it's associated with the development of other tumors as well.
Retinoblastoma can metastasize to other organs in the body.
So, this gene is something we think of in our typical two-hit hypothesis.
Remember, everyone has two copies of the retinoblastoma gene.
Here's a normal child who freakishly had one mutation in a cell population.
That population of cells then made a new set of clonal populations
and then they have freakishly another mutation.
This is the more common type where they're not born with a mutation
and this happens a little bit later in life because it takes more time to sort of -
through absurdly bad luck have two hits on both genes.
This is to be compared with someone who has inherited this problem.
They've inherited one copy already not working, in this case, it's on dead sperm.
And then they only need one hit before they develop the tumor,
so this would be more commonly in the 30% of children who have actually inherited the poor portion of the gene.
So how does it present?
Well in infants or later in childhood, it's going to typically present with leukocoria.
Sometimes patients notice in a photograph that one eye is red and the other one isn't.
Often, it's picked up on routine screening by doctors.
So leukocoria is a white reflection in the pupil in infancy.
It can also be associated with strabismus because these patients may not be seeing very well
and a decreased visual acuity.
They can also develop heterochromia of the iris as you can see here.
In general, these patients will get a CBC with differential
which can be abnormal if there is bone metastasis of the lesion.
We will also get an LP to assess for spread into the CNS.
What are the radiologic findings? Well, we usually sedate the patients
and do an ophthalmologic evaluation of both eyes under sedation.
We often will ultrasound the eyes to determine the extent of disease.
And we'll get a CT +/- an MRI of the orbits and brain to further characterize where this lesion is.
Lastly, we may get a bone scan if we're worried about boning metastasis
as a way of determining if there are any.
So how do we treat this tumor?
Well, we prefer if we can to do vision sparing techniques.
This will involve graduation, chemotherapy, surgery, photocoagulation, cryotherapy, and thermotherapy.
They were all a bunch of different ways the ophthalmologist can aggressively attack this disorder.
Unfortunately, there are times when we do have to do surgical
enucleation of the eye and we will remove the affected eye.
This is usually in unilateral cases.
We don't do this typically in cases of bilateral disease
because the risk is so profound that the other eye will be affected.
Complications are what you might expect from a germline mutation.
This is an inherited germline mutation, so in those minority of patients who have inherited,
they absolutely have risk for other malignancies for the rest of their life.
Vision loss is from surgery or from disease and that we can expect.
Additionally, for those who have a secondary malignancy,
there is a radiation risk of osteosarcoma and there can be also risk of skin cancer as well.
So that's a brief summary of retinoblastoma in childhood, thanks for your time.