Retinocytoma/retinoma: comparative analysis of clinical features in 78 tumors and rate of transformation into retinoblastoma over 20 years

Purpose: To explore clinical features and long-term outcomes in patients with retinocytoma/retinoma.

Methods: The medical records of patients with retinocytoma/retinoma over a 20-year period were reviewed retrospectively to compare patient age at presentation (<4 vs ≥4 years), tumor type, and tumor focality (unifocal vs multifocal).

Results: Of 2,021 patients with retinoblastoma, 62 (3%; median age, 5 years; 85% white; 58% male) had 78 tumors: 54 retinocytoma (69%) and 24 retinoma (31%). Median basal tumor diameter was 6.0 mm; mean thickness, 2.3 mm. Younger patients (<4 years) were more likely Hispanic (19% vs 2%; P = 0.04), with leukocoria (24% vs 0%; P = 0.003), and with calcification in ≤50% of the tumor (96% vs 70%; P = 0.007). Compared with retinoma, retinocytoma was more prevalent in older patients (median age, 9 vs 2 years; P < 0.001), with fewer symptoms (38% vs 69%; P = 0.04), larger median basal diameter (7.0 vs 3.0 mm; P < 0.001), greater thickness (2.5 vs 1.6 mm; P = 0.02), and less frequently with additional retinoblastoma in either eye (9% vs 71%; P < 0.0001). Compared with multifocal tumors, unifocal tumors occurred more frequently with lack of symptoms (62% vs 25%; P = 0.03), greater median basal diameter (6.0 vs 3.3; P = 0.003), and greater thickness (2.5 vs 1.5 mm; P = 0.006). Tumor transformation into retinoblastoma was found in 2.7% by 2 years, 9.2% by 5 years, 15.3% by 10-20 years. The only factor predictive of transformation was increasing thickness (P = 0.003; hazard ratio of 2.83 per 1 mm increase).

Conclusions: In our study cohort, the rate of retinocytoma/retinoma transformation into retinoblastoma increased from 2 to 10-20 years of age. The only factor predictive of transformation was increasing tumor thickness.