Orbital rule 4 : Retinoblastoma mimics lesions

1-From the name, this should be similar to retinoblastoma.

2-It is a group of intra ocular lesions occur in childhood with similar appearance of retinoblastoma but without calcium.

3-These diseases are:

-Coat's disease.

-Persistent hyper plastic primary vitreous.

-Retrolental fibroplasias.

4-All the above mentioned mimic retinoblastoma diseases have the following appearances:

-Increased density of vitreous in CT.

-Blood signal of vitreous in MRI.

-No calcification which is depicted clearly in CT.

5-D.D. of retinoblastoma mimics:

All the three lesions show vitreous hyper intensity in T1 and T2 MRI imaging.

All the three lesions show vitreous hyper density in CT imaging.

All the lesions does not show calcium in CT.

If the above mentioned criteria are fulfilled, then we proceed to look for the size of the globes, if it is equal or not.

If they are not equal in size, then look to the smallest one, if you find distorted lens with a retrolental mass with unilateral vitreous changes, so you are dealing with persistent hyper plastic primary vitreous.

If they are equal in size, then look to the changes seen in vitreous, if it is unilateral or bilateral.

If it is unilateral with normal lens and no retrolental mass, so you are dealing with Coat's disease.

But if it is bilateral vitreous changes with bilateral small globes, so you are dealing with retrolental fibroplasia.