Table 1. AQP1 expression increases with the progression from normal brain to low-grade to high-grade astrocytoma. The proportion of microvessels expressing AQP1 was graded 0 (⩽33%), +(34–66%) or ++(⩾67%). Astrocytes/astrocytoma cells were graded 0 (nil), +(mostly cell membrane), ++(mostly cell membrane and cytoplasm) for the pattern of AQP1 immunostaining and ⩽50%, >50% for the proportion of cells expressing AQP1.