Paediatric Imaging

Necrosis, fat

saponification of fat by tissue lipase after local destruction of fat cells with release of lipids and haemorrhage with fibrotic proliferation. It is seen in many tissues, often when a mass has outgrown its blood supply as occurs in tumour proliferation.

Fat necrosis occurs in the breast, for example, following direct external trauma and presents as a firm, slightly fixed mass. Ultrasonographically, it appears as a hypo/ anechoic mass with fairly well defined margins. If mammography is deemed necessary it characteristically shows as a well-circumscribed mass with translucent areas at the centre (oil cyst). It may also calcify (liponecrosis macrocystica calcificans) but these changes are difficult to see in the dense adolescent breast and MRI is preferable in doubtful cases. See neonatal fat necrosis

AM