To report the clinical characteristics of retinoblastoma patients whose diagnosis was difficult due to atypical ocular manifestations.

Among retinoblastoma patients who were diagnosed and treated from January 1999 to December 2014 at Seoul National University Children's Hospital, 6 patients whose diagnosis was difficult were retrospectively reviewed. Factors including age, sex, family history, initial findings, time to final diagnosis, histopathologic examination, additional treatment, and survival rate were evaluated.

Among 6 patients, 5 were male, and the mean age at the initial visit was 32.9 ± 19.1 months. None of the patients had family history, and all presented with unilateral lesion at the initial visit. The initial diagnoses were Coats' disease and uveitis in 2 patients, respectively, and persistent hyperplastic primary vitreous and traumatic hyphema in 1 patient, respectively. During an intensive short-term follow-up of 8.3 ± 5.3 weeks, 2 patients showed malignant cells after external subretinal fluid drainage procedure, and 4 patients demonstrated increasing ocular size or calcification in imaging. These patients received enucleation under suspicion of malignancy and were finally diagnosed with retinoblastoma after histopathologic examination. There were 2 patients with optic nerve involvement, and 3 patients underwent additional systemic chemotherapy. Five patients were followed-up for 7.6 ± 6.3 years after enucleation, and the mean age at final follow-up was 10.6 ± 7.4 years.

Retinoblastoma is one of the diseases in which early diagnosis and treatment are important. However, some cases are difficult to diagnose, even for experienced clinicians. If there are no typical manifestations such as mass or calcification and early findings show retinal detachment, glaucoma, pseudohypopyon, or hyphema, intensive short-term follow-up to exclude retinoblastoma is needed.