ABSTRACT
PURPOSE: To report four cases of spontaneous regression of retinoblastoma. METHODS: The clinical courses of two patients were retrospectively investigated: a patient who has been diagnosed with bilateral retinoblastoma and has survived more than six years after his parents refused treatment and a patient with bilateral retinal lesions who has survived nine years whose sister was treated for unilateral retinoblastoma. RESULTS: A nine-year-old girl, diagnosed with bilateral retinoblastoma when she was three months old, remained well for nine years after her parents refused to seek treatment. The right eye had three retinal masses that had regressed, and the left eye showed signs of phthisis and was enucleated for a cosmetic purpose. Microscopic examination of the left eye showed a mass, which consisted mostly of fibroblasts and ground substance and a few retinoblasts without mitotic figures. A six-year-old boy with a family history of retinoblastoma presented with regressed retinal masses in both of his eyes at the first funduscopic examination. The retinal lesions showed no change until his ninth year. CONCLUSIONS: Two cases of spontaneous regression of bilateral retinoblastoma were observed. No distant metastasis was detected during long-term follow-up. The retinal lesions were similar to regressed masses after treatment.