Macroadenomas, however, may also be heterogeneous in appearance due to necrosis, cystic degeneration or haemorrhage. Necrotic areas show as a lower signal than the surrounding tumour on T1-weighted images. Areas that progress to cystic degeneration show as a signal which is similar to CSF (i.e. low on T1-weighted images and high on T2-weighted images). Acute haemorrhage in these tumours is best seen as high density areas on non-contrast CT studies whilst sub-acute haemorrhage is easier to identify using MR studies, appearing as a high signal on T1-weighted images. Macroadenoma appearance on T2-weighted images varies (Fig. 24.10). A region of high signal intensity would suggest necrosis. Calcification, although rare, may also be seen and is usually curvilinear.
