Answers to Case 1-1-4
1. Axial (Fig1-1-4.1a ) and coronal (Fig. 1-1-4.1b ) non-contrast CT images of the
upper abdomen, and an ultrasound image (Fig.1-1-4.1c ) of the left kidney showing
an exophytic mass in the upper pole of the left kidney. This mass has similar
density to the subcutaneous and retroperitoneal fat on both CT and USS. The
diagnosis is angiomyolipoma (AML). Diagnosis can be made on CT (or MRI)
if the mass has a density of <0 HU (or is fatty on T1 MRI), but some atypical
fat-poor AMLs have a higher density.
2. AML is a hamartoma including various proportions of adipose tissue, spindle and
epithelioid smooth muscle and abnormal blood vessels. Approximately 80% are
solitary and sporadic, 20% are multifocal and associated with tuberous sclerosis.
Tuberose Sclerosis (TS), an inherited autosomal dominant syndrome, is caused by
mutation of either of two genes, TSC1 and TSC2 located on chromosomes 9q34
and 16p13, respectively. The vast majority of AMLs are benign, but rare malignant
variants have been described. Sporadic cases are more common in females (4:1);
there is no apparent sex predilection in TS patients. The increased incidence of
sporadic AML in females and their increased growth rate in pregnancy, the onset
of AML after puberty and progesterone immunoreactivity support a hormonal
infl uence.
3. The majority of tumours are asymptomatic, but symptoms include abdominal/
fl ank pain, hypertension, weight loss and nausea. Tumours >4 cm have an
increased risk of spontaneous haemorrhage (Wunderlich syndrome), which may
be catastrophic, and therefore this is usually deemed as the threshold for prophylactic
treatment – ideally with a nephron preserving procedure such as embolisation
or partial nephrectomy.
4. Figure 1-1-4.2a,b are arteriograms of the left renal artery before and after selective
embolisation of the branch feeding the AML. No residual fl ow is seen within
the vessel following embolisation, but the tumour can recur in the long term,
especially in patients with TS.
5. Figure 1-1-4.3 is the cut surface of a nephrectomy specimen showing a heterogeneous
mass expanding the upper pole and bulging into the hilum. The macroscopic
predominance of fat and the presence of obvious transected vascular
lumena is typical of AML. This diagnosis was confi rmed by the microscopic
identifi cation of all the tissues described in answer 2.