Post-radiation retinal infiltrates simulating recurrent retinoblastoma: a clinical and pathologic case report

An 8-month-old boy was found to have a sporadic unilateral stage IIa retinoblastoma, extending inferiorly and temporally from the right fovea. Within 5 weeks of diagnosis the tumor was treated with 4500 rads fractionated over 20 treatments. Examination under anesthesia (EUA) 1 month later revealed unequivocal clinical and echographic evidence of tumor regression. EUA 3 months after completion of radiation therapy revealed continued tumor regression with no evidence of new tumor formation. The third EUA, performed 6 months after radiation treatment, showed that multiple discreet gray-white retinal infiltrates had developed, predominantly in the area immediately below the regressed tumor. Because of concern that these lesions represented viable retinoblastoma, the eye was enucleated. Pathologic examination of these lesions revealed them to be collections of foamy cells containing melanin granules suggestive of pigment epithelial origin.