Angiomyolipoma

Angiomyolipoma is an important hamartomatous, benign renal parenchymal tumour:

• in the majority of cases the angiomyolipoma is asymptomatic. However it may present as an abdominal mass or with haematuria. The likelihood of an angiomyolipoma being symptomatic is higher with tumours greater than 4cm in diameter (1)
• it occurs in more than 50% of individuals with tuberous sclerosis. It also occurs sporadically and it is four times more common in women
• one study revealed an incidence of 0.25% in patients investigated via ultrasound in a department of internal medicine (2)

The tumour is composed of fat, blood vessels and smooth muscle. The fat has a characteristic tissue density that often permits easy identification of an angiomyolipoma on CT.

The majority of tumours can be managed conservatively, especially if they are asymptomatic. In some cases where the diagnosis is not established with imaging findings, partial nephrectomy enables pathologic diagnosis with a minimal loss of function. Resection of the tumour may be necessary for the relief of pain or haemorrhage. Selective arterial embolization is also a treatment option for haemorrhage (3). Radical nephrectomy may also be indicated in acute severe presentations e.g. massive haemorrhage.

There have been reports of malignant change in angiomyolipoma in patients without tuberous sclerosis (4,5) although this appears a rare occurrence and only the subject of case reports.

The association between renal cell adenocarcinoma and patients with tuberous sclerosis - a patient group where there is a recognized association with angiomyolipoma - has been investigated (6) and the authors conclude that 'analysis of the distribution of characteristics and incidence of; renal cysts, renal cell carcinoma, and lymph node involvement demonstrate no increased risk of renal cell carcinoma in patients with tuberous sclerosis complex (P = NS). Though anecdotal evidence has suggested a relationship between tuberous sclerosis complex and renal cell carcinoma, meta analysis of cases of coincident tuberous sclerosis complex renal complex, cystic changes, angiomyolipoma and renal cell carcinoma implies an identical, though small, risk of malignancy in tuberous sclerosis complex patients as compared with the normal population.'

Reference:

1. J Urol. 1993 Dec;150(6):1782-6.
2. Urologe A. 1994 Jan;33(1):68-72.
3. J Urol. 2002 Oct;168(4 Pt 1):1315-25.
4. Int J Urol. 2003 May;10(5):271-3.
5. Am J Surg Pathol. 2000 Jun;24(6):889-94.
6. Eur J Radiol. 1998 May;27(2):131-8.