Retinoblastoma is a tumor arising from retinal tissues of the eye. The condition can be inherited or spontaneous; the inherited form is associated with a mutation in the Rb1 gene.
Retinoblastoma is known to spread into the optic nerve and CSF. This image shows a retinoblastoma tumor clump. Notice the smaller size of the tumor cells. They are similar in appearance to acute lymphoblastic leukemia (ALL): L1.
Notice the clustering of these cells, which form a three-dimensional aggregate on the cytospin. While an L1 ALL might have similar N/C ratios with similar chromatin and cytoplasmic characteristics, L1 ALL will typically show a liquid distribution pattern on the cytospin with a more even distribution and without clumping.