Feulgen-positive deposits in retinoblastoma. Incidence, composition, and ultrastructure.

The incidence of hematoxyphilic extracellular deposits in 159 cases of retinoblastoma was found to be 18%. Six other features of these tumors also were examined. In the majority of eyes with these deposits, the tumors were composed solely of anaplastic cells. None was well differentiated with preponderantly rosette formation. The hematoxyphilic deposits were Feulgen-positive, and this staining was diminished but not abolished by pretreatment with purified deoxyribonuclease (DNase), which did abolish nuclear staining. Feulgen staining of the deposits was totally blocked by pronase--DNase pretreatment--suggesting that the deposits may represent DNA-protein complexes. Ultrastructurally, these deposits were electron dense and finely vacuolar. The deposits may originate from degenerating tumor cell nuclei, and the possibility that they may represent immune complexes warrants future study in view of occasional spontaneous regression of this tumor.