Eble JN, Sauter G., Epstein JI, Sesterhenn IA - iarc

Angiomyolipoma
G. Martignoni
M.B. Amin
Definition
Angiomyolipoma (AML) is a benign mesenchymal
tumour composed of a variable
proportion of adipose tissue, spindle and
epithelioid smooth muscle cells, and abnormal
thick-walled blood vessels.
ICD-O code 8860/0
Epidemiology
Age and sex distribution
In surgical series which are usually overrepresented
by non-tuberous sclerosis
(TS) cases there is a 4:1 female predominance
{1299,1825,2503,2628}, but there
is no apparent sex predilection in TS
patients with AML detected by imaging
techniques {487}. The mean age at diagnosis
in surgical series is between 45
and 55 for patients without TS and
between 25 and 35 for those with TS
{1299,1825,2503,2628}. It is possible
that puberty influences the development
of AML {487}.
Incidence
AMLs account for approximately 1% of surgically
removed renal tumours. It has been
considered an uncommon neoplasm, but
its frequency is increasing because it is
detected in ultrasonographic examinations
performed to evaluate other conditions
{816}. It can occur sporadically or in
patients with TS, an inherited autosomal
dominant syndrome {910}. Most surgical
series report four times as many sporadic
AMLs as AMLs associated with TS {1299,
1825,2503,2628}.
Etiology
AML is believed to belong to a family of
lesions characterized by proliferation of
perivascular epithelioid cells (PEC) {268,
269,785,917,1171,2707,2920}. Recent
molecular studies have demonstrated its
clonality {933,2008}, and immunohistochemical
and ultrastructural studies support
the idea of histogenesis from a single
cell type {269,1103,2511,2570,2920}.
The etiology and pathogenesis of the
neoplasm are unknown. The different frequency
of AML in females and males in
the surgical series, the onset of AML after
puberty and the frequent progesterone
receptor immunoreactivity in AML {1077}
suggest a hormonal influence.
Localization
AMLs may arise in the cortex or medulla
of the kidney. Extrarenal growth in the
retroperitoneal space with or without
renal attachment can occur. Lesions may
be multifocal {2570}. Multifocal AML in
the kidney indicates a presumptive diagnosis
of TS.
Fig. 1.94 Angiomyolipoma of the kidney. CT scan of
angiomyolipoma characterized by high fat content.
Clinical features
Signs and symptoms
Clinical features differ, depending on the
presence or absence of TS. In TS, AMLs
are usually asymptomatic and discovered
by radiographic screening techniques.
Patients without TS present with
flank pain, haematuria, palpable mass,
or a combination of these signs and
symptoms. Retroperitoneal haemorrage
may occur {2503}. Simultaneous occurrence
of AML with renal cell carcinoma
(RCC) and oncocytoma in the same kidney
has also been reported {1224}.
Another interesting aspect of AML is the
association with lymphangioleiomyomatosis
(LAM), a progressive disease
which usually affects the lungs of young
women and which is also related to TS.
Histopathological and genetic studies
have demonstrated that AML and LAM
share numerous features {268,2909}.
Imaging
Computerized tomography (CT) and
ultrasonography permit the preoperative
diagnosis of AML in almost all cases.
High fat content, which is present in most
AMLs, is responsible for a distinctive pattern
on a CT scan. Tumours composed
predominantly of smooth muscle cells or
with an admixture of all three compo-
A
B
Fig. 1.95 A Angiomyolipoma. Large tumour with hemorrhagic component. B A large tumour with high lipid content, bulging into the perirenal fat is seen. Match with
CT. C Multiple angiomyolipomas of the kidney.
C
Renal angiosarcoma / Malignant fibrous histiocytoma / Angiomyolipoma
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