are hamartomatous lesions containing smooth muscle, blood vessels and
mature adipose tissue.
Angiomyolipoma occurs most
frequently in the kidneys.
This tumour has been reported in several other organs, including the liver, reproductive
organs, skin, and retroperitoneum.
Cases have been reported in the colon, duodenum, stomach,
These mesenchymal tumours
arise from the perivascular epithelioid cell (PEC), which may
give rise to a variety of tumours and proliferations such as
angiomyolipoma, lymphangiomyoma, lymphangiomyomatosis, clear
cell myomelanocytic tumour of the falciform ligament/ligamentum
teres, and pulmonary clear cell "sugar" tumour.
Grossly, the tumour is
yellow to gray depending on the relative proportion of the various tissue
tumour consist of three components: mature fat cells, blood vessels, and
smooth muscle cells.
Histopathology image of
Immunohistochemically, the proliferating smooth
muscle cells are positive for vimentin, alpha-smooth muscle actin, and
also express the melanocytic markers HMB-45, MART-1 (Melan A),
microphthalmia transcription factor, and tyrosinase.
Angiomyolipoma may be
associated with Tuberous Sclerosis .
Although classic renal
angiomyolipomas were regarded as universally benign lesions it
is becoming increasingly clear that PEComas should be regarded
as tumours of uncertain malignant potential.
with a poor outcome are usually monotypic myomatous variants,
especially those with dominant pleomorphic epithelioid
Factors likely to
indicate poor outcome include presence of haemorrhage and
necrosis, local invasiveness, and high mitotic activity.