Annals of the Royal College of Surgeons of England (1992) vol. 74, 144-148
Angiomyolipoma of the kidney: a clinical enigma in diagnosis and management Amir V Kaisary
Kit Wong MB BS FRCS Surgical Registrar
MS FRCS
Consultant Urologist
University Department of Surgery, The Royal Free Hospital, London
Catherine M Waters
MB BS
Joseph Horner
FCS(SA) FRCSEd
Consultant Surgeon
Surgical House Officer
Department of Surgery, Ashford Hospital, Ashford, Middlesex
Michael J Hershman
MS FRCS
Senior Registrar in Surgery
St Mary's Hospital, London
Key words: Angiomyolipoma; Radical nephrectomy; Renal preserving surgery
Renal angiomyolipomas are uncommon benign tumours which clinically mimic renal cell carcinoma. They have characteristic features on ultrasound and CT scanning which may enable their diagnosis preoperatively. We review our experience of six cases of renal angiomyolipoma. These cases highlight the difficulties in making a preoperative diagnosis despite the use of modern scanning. We advocate conservative resection when the diagnosis is made preoperatively and when technically possible, but radical nephrectomy should be performed if there is a possibility of a carcinoma.
recently, refinement in computed tomography and ultrasonography have enabled accurate preoperative diagnosis (1,2) and has made renal-preserving operations possible (3). We report six patients with angiomyolipoma. None had stigmata nor family history of tuberous sclerosis. These cases illustrate the difficulty in making accurate preoperative diagnosis despite the use of modern scannmg facilities.
Case reports Case I
Renal angiomyolipomas are rare benign tumours composed of thick-walled blood vessels, fully differentiated smooth muscle and adipose tissue. Two distinct clinicopathological entities exist depending on their association with tuberous sclerosis. When renal angiomyolipomas occur in patients with tuberous sclerosis they are often bilateral, small, multiple and asymptomatic. Conversely, angiomyolipomas not associated with tuberous sclerosis present as unilateral, large and symptomatic tumours. Preoperative diagnosis is often difficult as they can mimic renal cell carcinoma clinically and radiologically. More
Correspondence to: Mr K Wong, Department of Cardiothoracic Surgery, The London Chest Hospital, Bonner Road, London E2 9JX
A 63-year-old woman was incidentally found to have a right loin mass by her general practitioner. She had no history of loin pain or haematuria. Physical examination revealed a firm, mobile, non-tender 15 cm mass in the right loin. An intravenous urogram confirmed a mass lesion in the lower half of the right kidney. An abdominal ultrasound revealed a hyperechogenic dumbell-shaped mass in the kidney. Laparotomy revealed a large mass arising from the lower pole of the right kidney with no evidence of metastases. A right radical nephrectomy was performed. Macroscopic examination revealed three nodular tumours in the lower pole of the right kidney measuring 3 cm x 2 cm, 4 cm x 3 cm and 12 cm x 9 cm x 8cm. Histological appearances were consistent with angiomyolipoma. The patient remains well 5 years later.
Angiomyolipoma of the kidney Case 2 A 68-year-old woman was admitted having collapsed with left loin pain. She had previously been well. On examination, she was shocked, with a systolic blood pressure of 60 mmHg and had left loin tenderness and a palpable loin mass. Urinalysis showed traces of blood. Her haemoglobin was 7.2 g/dl. She was resuscitated and remained cardiovascularly stable. An abdominal ultrasound and computed tomography (CT) showed a mass in the lower pole of the left kidney with surrounding perirenal haemorrhage. She was also shown to have a 2 cm x 2 cm lesion in the upper pole of the right kidney. This lesion had an area of low attenuation compatible with fat ( - 40 Hounsfield units) and was consistent with a benign tumour. Laparotomy revealed a large retroperitoneal haematoma with a haemorrhagic tumour in the lower pole of the left kidney. A left radical nephrectomy was performed. The tumour in the right kidney was palpably benign. Postoperative recovery was complicated by acute renal failure, but the patient subsequently made an uneventful recovery. Pathological examination showed the 10 cm x 9 cm tumour to be an angiomyolipoma. The patient remains well 2 years later and her right renal tumour, which is thought to be an angiomyolipoma, has shown no progression on serial CT scanning.
Case 3 A 29-year-old woman presented with a 3-year history of intermittent episodes of left loin pain. This had worsened 6 weeks before admission. Abdominal examination revealed a firm, tender mass in the left loin. Urinalysis showed moderate traces of blood. She had a haemoglobin of 6.1 g/dl with a mean corpuscular volume (MCV) of 67. An intravenous urogram revealed a space-occupying lesion in the upper pole of the left kidney which had compressed and splayed the lower calyces. A CT scan confirmed a mass in the upper pole of the kidney with perirenal haemorrhage. There were some areas of low attenuation (-40 Hounsfield units), but the appearances were more suggestive of a renal cell carcinoma. Laparotomy revealed a large left renal mass arising from the upper pole with enlarged para-aortic lymph nodes. A radical nephrectomy was performed with an en bloc resection of the para-aortic nodes. A splenectomy was performed as the tumour was adherent to the spleen. Macroscopic examination showed a large haemorrhagic tumour measuring 16 cm x 13 cm x 10 cm. There was tumour extension into the perinephric fat. Histological appearances were consistent with an angiomyolipoma. The para-aortic lymph nodes had similar islands of tumour deposit. The patient made an uneventful postoperative recovery and is well 6 months later.
Case 4 A 55-year-old woman presented with a sudden severe attack of left loin pain. Physical examination revealed left
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loin tenderness but no palpable masses. Urinalysis was negative. An abdominal ultrasound showed a partly cystic and solid mass in the upper pole of the right kidney. A CT scan confirmed this and the appearances were suggestive of either a renal cell carcinoma or a haemorrhage into a cyst. An arteriogram of the kidney demonstrated an abnormal tumour circulation in the left upper pole. A left radical nephrectomy was performed with an en bloc removal of the para-aortic nodes. Macroscopic appearances were of a 4 cm x 5 cm cystic, haemorrhagic mass in the upper pole and several other yellow/white nodules. The histology of these lesions was of an angiomyolipoma, though many of the cells did show marked nuclear pleomorphism and mitotic figures. There was extension of the tumour into the perirenal fat and hilar lymph nodes were replaced by the tumour. The patient remains well 3 years after her operation.
Case 5 A 36-year-old woman, whilst on holiday abroad, was admitted with severe right loin pain and found to be in hypovolaemic shock. She was treated conservatively. On her return she had an ultrasound scan which showed a lesion in the lower pole of the right kidney, which had a cystic component as well as a hyperechogenic component anteriorly. Her CT scans showed a lesion which was impossible to distinguish from renal cell carcinoma, haemorrhage from an angiomyolipoma, or a large renal cyst. A renal angiogram showed an abnormal tumour circulation. A right radical nephrectomy was performed. Pathological examination revealed a 5 cm x 6 cm angiomyolipoma. The patient remains well 3 years later.
Case 6 A 41-year-old Iraqi man was referred for further management of a retroperitoneal tumour found at laparotomy. The patient had presented initially with pyrexia, right loin pain and an ultrasound scan revealed a fluid collection behind the right kidney. This was thought to be a perinephric abscess. The patient was started on antibiotics and a laparotomy performed to surgically drain the abscess. At laparotomy, a small, friable, fleshy tissue mass measuring 3 cm x 3 cm was found behind the hilum of the right kidney. The mass was completely excised and did not appear to arise from the kidney or its hilum. This tumour was thought initially to be a malignant fibrous histiocytoma, but review of the histological slides by our pathologist revealed that the appearances were in fact those of an angiomyolipoma. The patient remains asymptomatic 2 years later.
Discussion Angiomyolipoma of the kidney is a rare benign tumour with a reported incidence of 0. 1-2.1% among surgically
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Table I. Presenting features and pathological findings in six patients with angiomyolipoma
Pain
Palpable mass
Shock
Haematuria
Site (M = multiple lesions)
Case 1
-
+
-
-
M; Lower pole
Case 2 Case 3 Case 4
+ + +
+ +
+
-
-
+ + -
Lower pole Upper pole M; Upper pole
Case S Case 6
+ +
-
-
-
Lower pole Extrarenal
treated renal tumours (4-6). Angiomyolipoma not associated with the tuberous sclerosis complex occurs unilaterally, is solitary and has a female to male ratio of 4:1 (7). The age of presentation is commonly between 40 and 60 years (8). Five of our patients were women and all presented between the 3rd and 6th decades of life. The presentation of this tumour in the absence of the tuberous sclerosis complex can be variable and clinically indistinguishable from renal cell carcinoma (Table I). The classical presentation is of loin pain, haematuria and a palpable mass, though patients can be asymptomatic (9). Patients may, however, present more dramatically in shock and loin pain due to the spontaneous rupture of the tumour. This is an uncommon presentation, occurring in 5-10% of cases in the literature (10-11), though it is the second commonest cause of a spontaneous rupture of the kidney after renal cell carcinoma (12). The unusual nature for which angiomyolipomas can present is highlighted in Case 6. The patient had symptoms of loin pain and a pyrexia which was thought to be due to a perinephric abscess. Histology later confirmed the extrarenal tumour to be an angiomyolipoma, and in retrospect the pyrexia was probably a result of tumour necrosis. Extrarenal angiomyolipomas in the absence of the tuberous sclerosis complex are uncommon. In a recent review, Randazzo et al. (13) found that only 24 cases had been reported previously. In our case the tumour was found behind the hilum of the kidney, though not arising from the kidney. The preoperative diagnosis of these tumours is difficult. Intravenous urography and angiographic findings are often not discernible from renal cell carcinoma. More recently, the combined imaging of computed tomography (CT) and ultrasonography has been used to make an accurate preoperative diagnosis of an angiomyolipoma (1-3,14). The classical findings are of low attenuation areas of fat on computed tomography (Fig. 1) and hyperechogenicity on ultrasonography (Fig. 2) from the multiple fat and non-fat interfaces within the tumour. However, not all angiomyolipomas demonstrate these findings. Perirenal haemorrhage may distort the CT findings. The diagnosis of angiomyolipoma was considered in only two of our patients. In retrospect, one other patient had typical findings on ultrasonography or
Size (cm)
Lymph
3x2, 4x3 12x9x8 1Ox9 16 x 13 x 10 4 x 5, small nodules 5x66 3x 3
nodes
+ +
Figure 1. CT scan of the abdomen showing low attenuation areas of fat within the tumour. There is also haemorrhage seen around the tumour.
computed tomography (Table II). With greater awareness, it may be possible to distinguish renal cell carcinoma from angiomyolipoma. The classical hyperechoTable II. Radiological findings in the six cases. The majority of patients had findings which were indistinguishable from renal cell carcinoma though some features of angiomyolipoma were present Appearance at Case No.
Ultrasound
1 2 3
Typical Atypical Atypical
Atypical Some features
4
Atypical
Some features
5
Typical
Some features
6
Atypical
Atypical
CT scan
Preoperative diagnosis RCC RCC RCC AML RCC Haemorrhage into a cyst or AML RCC AML Perinephric abscess
RCC = renal cell carcinoma. AML = angiomyolipoma
Angiomyolipoma of the kidney
Figure 2. Longitudinal view on renal sonography shows the characteristic echogenic mass.
genic finding on ultrasonography may alert the radiologist to specifally look for small areas of fat on CT (1). Lipomas or liposarcomas may also show areas of fat on CT, but lipomas contain more fat while liposarcomas are larger, may be invasive and would warrant surgical resection because of their size. The management of renal angiomyolipoma has changed over the last decade. The possibility of making correct radiological diagnosis has encouraged a conservative approach. Surgeons have advocated renal-preserving surgery and a policy of observation whenever possible (3,15). However, a radiological diagnosis is not always possible, as has been highlighted in our series. Another problem in observing these tumours is predicting those which will remain asymptomatic. A high proportion of these tumours produce symptoms. In the literature, approximately 25% of patients presented symptomatically with serious complications (9). In a recent review, Oesterling et al. (16) found that 77% of lesions of 4 cm or less were asymptomatic and they recommended intervention for symptomatic lesions >4 cm. In our own series, one patient had symptoms (Case 6) with a 3 cm lesion and it may be difficult to predict the natural history of the tumour on size alone. Another concern in observing patients with angiomyolipomas is the risk of missing a synchxonous carcinoma. The incidence of this is rare though there have been several case reports (17-20). In their series, McBlute et al. (3) found 1 in 4 patients with tuberous sclerosis and 2 in 29 patients (7%) without tuberous sclerosis to have a synchronous carcinoma. This would, in fact, encourage early surgical intervention. The management of renal angiomyolipomas should therefore be individualised. Symptomatic and large tumours require surgical intervention. Smaller (< 3 cm), asymptomatic tumours may be observed, but require close monitoring by serial CT scanning. Lesions found to be increasing in size, showing calcification or any radiological signs of malignancy should always be treated surgically. Renal-preserving surgery should be performed if radiological diagnosis is certain and whenever surgically possible. However, radical nephrectomy
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Figure 3. Typical histological features are of smooth muscle, blood vessels and adipose tissue (original magnification x 400).
should be the procedure of choice if there is a suspicion of malignancy. Angiomyolipomas are composed of mature fat cells, smooth muscle and blood vessels with thickened walls (Fig. 3), though they can possess other histological features which may mimic malignancy. Cases 3 and 4 showed infiltration of the tumour into adjacent perirenal fat and surrounding structures. Cases 1 and 3 had multiple 'satellite' lesions which are unusual in patients without tuberous sclerosis. Cases 3 and 4 also demonstrate the multicentricity of the tumour with replacement of adjacent nodes with the tumour (21). Cellular atypia and mitotic figures were also seen in Case 4. All these features may be characteristics of malignant tumours, but are typical pathological findings in angiomyolipomas. These tumours will always present a difficult problem in preoperative diagnosis. However, this should improve with an increased clinical awareness and refinement in radiological scanning. This would enable renalpreserving operations to be performed whenever possible.
Refereuces I Bosniak MA, Megibow AJ, Hulnick DH, Horii S, Raiendra N. CT diagnosis of renal angiomyolipoma: the importance of detecting small amounts of fat. AJR 1988;151:497-501. 2 Bosniak MA. Angiomyolipoma (hamartoma) of the kidney: a preoperative diagnosis is possible in virtually every case. Urol Radiol 1985;3:135. 3 McBlute ML, Malek RS, Segura jW. Angiomyolipoma: clinical metamorphosis and concept for management. J Urol 1988;139:20-4. 4 Nurmi MJ, Katevuo K, Ekfors T, Puntala PV. Diagnosis and treatment of renal angiomyolipoma. Scand J Urol Nephrol 1986;20:289-94. 5 Farrow GM, Harrison EG Jr, Utz DC, Jones DR. Renal angiomyolipoma: clinico-pathologic study of 32 cases. Cancer 1968;22:564 7. 6 HIadju SI, Foote FW. Angiomyolipoma of the kidney: a report of 27 cases and a review of the literature. J Urol 1969;102: 396.
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7 Kavaney PB, Fielding I. Angiomyolipoma and renal cell carcinoma in the same kidney. Urology 1975;6:643-6. 8 Allen T, Risk W. Renal angiomyolipoma. J Urol 1965;94: 203-7. 9 Wong AL, McGeorge A, Clark AH. Renal angiomyolipoma: a review of the literature and a report of 4 cases. Br J Urol 1981;53:406-11. 10 Kaneti J. Rupture of renal angiomyolipoma: conservative surgery. J Urol 1983;129:810-11. 11 Valvo JR. Spontaneous intrapartum rupture of renal hamartoma. Urology 1983;22:286-9. 12 McDougal WS, Kursh ED, Persky L. Spontaneous rupture of the kidney with perirenal haematoma. J Urol 1975;114: 181-4. 13 Randazzo RF, Neustein P, Koyle MA. Spontaneous perinephric haemorrhage extrarenal angiomyolipoma. Urology 1987;29:428-31. 14 Uhlenbrock D, Fischer C, Beyer HK. Angiomyolipoma of the kidney: comparison between MRI, computed tomography and ultrasonography for diagnosis. Acta Radiologica 1988;29: 523-6. 15 Pode D, Meretik S, Shapiro A, Caine M. Diagnosis and management of renal angiomyolipoma. Urology 1985;25: 461-7.
16 Oesterling JE, Fishman EK, Goldman SM, Marshall FF. The management of renal angiomyolipoma. J Urol 1986; 135:1121. 17 Silpananta P, Michel RP, Oliver JA. Simultaneous occurrence of angiomyolipoma and renal cell carcinoma: clinical and pathologic (including ultrastructural) features. Urology 1984;23:200. 18 Tanaka T, Hisa T, Morimoto K et al. Association of renal angiomyolipoma and renal cell carcinoma: preoperative diagnosis. EurJ7 Radiol 1982;2:92. 19 Takeyama M, Arima M, Sagawa S, Sonada T. Preoperative diagnosis of coincident renal cell carcinoma and renal angiomyolipoma in non-tuberous sclerosis. J Urol 1982; 128:579. 20 Schujman E, Meiraz D, Liban E, Servadio C. Mixed renomedullary tumour: renal cell carcinoma associated with angiomyolipoma. Urology 1981;17:375. 21 Busch FM, Bark CJ, Clyde HR. Benign renal angiomyolipoma with regional lymph node involvement. J Urol 1976;116:715-17. Received 19 June 1991
Assessor's comment This is an interesting little review of a little-known tumour of the kidney which brings out most of the main points. I have just finished doing a chapter for a forthcoming textbook on this and other tumours, and wish it had been available to me when I needed it. I think the general surgical readers of the Annals will find it of interest, mainly because angiomyolipoma is one of the most important causes of spontaneous retroperitoneal bleeding, and few of us know much about it. It is of
particular interest also because the Friends of Tuberous Sclerosis are sending a circular to everyone with an excellent summary of the literature-and it will make many of us wonder about angiomyolipomas and what we should be doing about one when we find it. JOHN BLANDY FRCS Professor Department of Urology The London Hospital