ObjectiveTo evaluate the pathological features of bilateral retinoblastoma (RB) and the relationship between different treatments and high-risk histopathologic features (HHF). MethodsRetrospective series of case studies. From 1999 to 2018, 73 patients with binocular RB diagnosed by pathological examination in Department of Ophthalmology, Peking University People's Hospital were included in the study. Among them, 50 patients were male (68.5%, 50/73), 23 patients were females (31.5%, 23/73); 11 patitents had a family history of RB. The mean age at the first diagnosis was 14.8±15.6 months. The average time between first diagnosis and first intervention was 3.97±4.74 months. According to the international classification standard of intraocular RB staging, among the 73 eyes, C, D and E stages were 2 (2.7%, 2/73), 15 (20.5%, 15/73), and 56 (76.7%, 56/73) eyes, respectively. Ocular images for each patient were obtained using a wide-angle contact fundus camera during examination under general anaesthesia. The treatment protocol (globe salvaging or enucleation) depended on the result of several clinical features. Globe salvaging treatment included chemotherapy combined with local therapy such as intra-arterial chemotherapy (IAC), intravitreal chemotherapeutics injection, cryotherapy, laser, transpupillary thermotherapy and radiotherapy. If globe salvaging failed, enucleation was offered and histopathologic analysis was conducted of the enucleated eye, the ophthalmic pathologist read and evaluated the presence of HHF. Independent samples t-test was performed to compare the continuous variables. The pathological features and the relationship between different treatments and HHF were analyzed. Group difference was calculated with chi-square. Results Among the 73 eyes, the first treatment was enucleation in 21 eyes (28.8%, 21/73); 52 eyes (71.2%, 52/73) were treated with eye protection. After enucleation, 9 cases (12.3%, 9/73) had recurrence and metastasis, and 7 cases (9.6%, 7/73) died. The intervention time of patients with recurrence and metastasis and those without recurrence and metastasis were 7.4±7.3 and 3.5±4.1 months respectively; the first intervention time of patients with recurrence and metastasis was significantly later than that of patients without recurrence and metastasis, but the difference was not statistically significant (t=－1.561, P=0.154). The pathological examination results showed that there were 26 eyes (35.6%, 26/73) with HHF, 4 (26.7%, 15/26) and 22 (39.3%, 22/56) eyes were in stage D and E, respectively. Those who received other treatments before enucleation had lower HHF percentages after enucleation than those who did not receive corresponding treatments, but the difference was not statistically significant (χ2=1.852, 0.074, 0.000, 1.007, 0.007, 2.729; P＞0.05). Among the 26 eyes, 5 (83.3%, 5/6) and 21 (31.3%, 21/67) eyes were treated with systemic chemotherapy combined with and without IAC, respectively, and there was a significant difference in the percentage of HHF (χ2=4.422, P=0.035). ConclusionsIAC eye-preserving therapy before enucleation has a significant effect on HHF.