Histopathologic grading of anaplasia in retinoblastoma

To determine whether the degree of tumor anaplasia has prognostic value by evaluating its correlation with high-risk histopathologic features and clinical outcomes in a series of retinoblastoma patients.

Retrospective clinicopathologic study.

The clinical and pathologic findings in 266 patients who underwent primary enucleation for retinoblastoma were reviewed. The histologic degree of anaplasia was graded as retinocytoma, mild, moderate, or severe as defined by increasing cellular pleomorphism, number of mitoses, nuclear size, and nuclear hyperchromatism. Nuclear morphometric characteristics were measured. The clinical and pathologic data of 125 patients were compared using Kaplan-Meier estimates of survival. Fisher exact test and multivariate regression were used to analyze the association between anaplasia grade and high-risk histologic features.

Increasing grade of anaplasia was associated with decreased overall survival (P = .003) and increased risk of metastasis (P = .0007). Histopathologic features that were associated with anaplasia included optic nerve invasion (P < .0001), choroidal invasion (P < .0001), and anterior segment invasion (P = .04). Multivariate analysis considering high-risk histopathology and anaplasia grading as predictors of distant metastasis and death showed that high-risk histopathology was statistically significant as an independent predictor (P = .01 for metastasis, P = .03 for death) but anaplasia was not (P = .63 for metastasis, P = .30 for death). In the absence of high-risk features, however, severe anaplasia identified an additional risk for metastasis (P = .0004) and death (P = .01).

Grading of anaplasia may be a useful adjunct to standard histopathologic criteria in identifying retinoblastoma patients who do not have high-risk histologic features but still have an increased risk of metastasis and may need adjuvant therapy.