Solitary astrocytic hamartoma simulating retinoblastoma.

The clinical, ultrasonographic and histopathological features (including immunohistochemistry and transmission electron microscopy) are described in a solitary astrocytic hamartoma of the retina in a 3-year-old child who was otherwise normal. Focal calcification was detected by ultrasound and this contributed to a misdiagnosis of retinoblastoma. The small tumour was located within the nerve fibre layer at the posterior pole and consisted solely of uniformly distributed astrocytes with benign cytological characteristics. Calcospherites were found within the cytoplasm of the astrocytes. Vascular abnormalities included intimal fibroplasia of arterioles with calcification of the internal elastic lamina and widespread endothelial proliferation; such abnormalities have not been previously noted in tumours with this degree of differentiation. The histological features are compared with those in previous reports of this rare tumour.