**3.6 Histopathology of retinoblastoma in enucleated globes following treatment**

The well-differentiated part of the RB is relatively radioresistant and chemoresistant; therefore, photoreceptor differentiation is more common in the enucleated eyes after radiotherapy or chemotherapy [11].

The histopathological examination of the enucleated eyes with RB after chemoreduction therapy may show Type 1, cottage cheese; Type 2, fish flesh; Type 3, combination of types 1 and 2; and Type 4, complete regression or presumably viable histologically intact tumor cells [3, 41, 42]. Type 2 regression pattern may have the same histological features as a retinocytoma and result in a retinocytomalike clinical appearance, which may be because well-differentiated tumors are relatively resistant to chemotherapy and therefore the cells are not cycling [42]. Similar regression patterns are also seen in tumors treated by intra-arterial chemotherapy (IAC) [43].
