Photoreceptor differentiation in retinoblastomas and its significance in prognosis.

Fleurette is an expression of photoreceptor differentiation and its presence is said to indicate a good prognosis. Twenty-four eyes from 22 cases of retinoblastoma sent to the Mitrani Foundation laboratory between the years 1964 and 1976 were reviewed histologically and clinically. The presence of differentiation in the tumour was not always associated with a good prognosis. The most important prognostic factor seemed to be the length of time the tumour is allowed to remain in the eye. The longer it remains the more undifferentiated the tumour cells become and the greater the probability that it will spread into the choroid and the optic nerve and out of the eye through the sclera and metastasise throughout the body. The presence of gliosis seems to improve the prognosis.