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{{Angiomyolipoma}}
{{Angiomyolipoma}}
{{CMG}}''' Associate Editor-In-Chief:''' {{CZ}}, {{Faizan}}
{{CMG}} {{AE}}{{CZ}}, {{Faizan}}, {{Rekha}}
 
==Overview==
==Overview==
'''Angiomyolipoma''' is a benign [[kidney|renal]] neoplasm previously considered to be a [[hamartoma]] or choristoma, but now known to be [[neoplastic]].<ref>Eble JN. Angiomyolipoma of the kidney. Semin Diagn Pathol 1988;15:21-40</ref> It is composed of variable amounts of [[fat]], [[Blood vessel|vascular]], and [[smooth muscle]] elements. The fat density of the tumour on [[CT]] has been regarded to be [[pathognomonic]], although there are now case reports of renal cell carcinoma types also possessing macroscopic fat. The lesion is well demarcated and contains mature elements. It occurs in more than 50% of individuals with [[tuberous sclerosis]], often bilaterally. Angiomyolipomata also occur in 40% of women who have a rare, cystic lung disease called lymphangioleiomyomatosis, or LAM.<ref name="pmid16915145">{{cite journal |author=McCormack FX |title=Lymphangioleiomyomatosis |journal=MedGenMed |volume=8 |issue=1 |pages=15 |year=2006 |pmid=16915145 |pmc=1682009 |doi= |url=http://www.medscape.com/viewarticle/518317}}</ref>
[[Angiomyolipoma]] is a [[benign]] [[kidney|renal]] [[neoplasm]] previously considered to be a [[hamartoma]] or choristoma, but now known to be [[neoplastic]]. It is composed of variable amounts of [[fat]], [[Blood vessel|vascular]], and [[smooth muscle]] elements. The [[fat]] density of the tumor on [[CT]] scan has been regarded to be [[pathognomonic]]. The [[Lesions|lesion]] is well demarcated and contains mature elements. It occurs in more than 50% of individuals with [[tuberous sclerosis]], often bilaterally. On [[gross pathology]], well circumscribed and uniform yellow [[mass]] is characteristic finding of [[angiomyolipoma]]. [[Angiomyolipoma]] is caused by a defect in the ''[[TSC1]]'' [[gene]]. [[Angiomyolipoma]] must be differentiated from [[retroperitoneal liposarcoma]], [[adrenal myelolipoma]], and [[renal cell carcinoma]]. If left untreated, small [[Angiomyolipoma|angiomyolipomas]] and those without dilated [[Blood vessel|blood vessels]] ([[Aneurysm|aneurysms]]) cause few [[symptoms]]. Small [[Angiomyolipoma|angiomyolipomas]] are associated with the most favorable [[prognosis]]. Common [[complications]] of [[angiomyolipoma]] include [[infection]], [[hematuria]] and [[hemorrhage]]. [[Abdominal]] [[Computed tomography|CT]] scan may be [[diagnostic]] for [[angiomyolipoma]]. On [[CT scan]], [[angiomyolipoma]] is characterized by smooth [[tumor]] margin with low intratumoral [[fat]] component and homogenous enhancement on both corticomedullary and excretory phase scans. [[Surgery]] is not the first-line treatment option for patients with [[angiomyolipoma]]. Transcatheter [[arterial]] [[embolization]] is usually reserved for patients with complicated [[disease]].
 
==Historical Perspective==
[[Angiomyolipoma]] was first described as a [[tumor]] in 1911 by Fisher. He also noted and described its association with the [[Tuberous sclerosis|Tuberous Sclerosis]]. It has been named as [[Angiomyolipoma]] by Morgan and associates in 1951.


==Classification==
==Classification==
[[Angiomyolipoma]] may be classified according to etiology into: [[tuberous sclerosis]] associated and isolated angiomyolipoma.
[[Angiomyolipoma]] may be classified according to [[Radiological|radiologic]] appearance into 7 subtypes: classic [[angiomyolipoma]], triphasic [[angiomyolipoma]], fat poor [[angiomyolipoma]], hyperattenuating [[angiomyolipoma]], isoattenuating [[angiomyolipoma]], [[angiomyolipoma]] with epithelial [[Cyst|cysts]], and [[angiomyolipoma]] in [[lymphangioleiomyomatosis]].


==Pathophysiology==
==Pathophysiology==
On [[gross pathology]], well circumscribed and uniform yellow mass are characteristic findings of [[angiomyolipoma]].
On [[gross pathology]], well circumscribed and uniform yellow [[mass]] is characteristic finding of [[angiomyolipoma]]. The components of an [[angiomyolipoma]] include vascular cells, immature [[smooth muscle cells]] and [[fat]] [[Cell (biology)|cells]]. [[Angiomyolipoma]] is caused by a defect in ''[[TSC1]]'' [[gene]]. Diseases associated with [[angiomyolipoma]] include [[von Hippel-Lindau syndrome]] and [[tuberous sclerosis]]. [[Cytological|Cytologic]] features of [[angiomyolipoma]] include round nuclei and bland [[chromatin]]. [[Immunohistochemistry]] markers of [[angiomyolipoma]] include positive [[Melanoma|melanocytic]] markers.


==Causes==
==Causes==
[[Angiomyolipoma]] is caused by a defect in the ''[[TSC1]]'' gene. It can also be caused by a defect in another gene:''[[TSC2]]''.
[[Angiomyolipoma]] is caused by a [[mutation]] in the ''[[TSC1]]'' gene. It can also be caused by a defect in ''TSC2'' [[gene]].


==Differentiating Angiomyolipoma from other Diseases==
==Differentiating Angiomyolipoma from other Diseases==
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==Epidemiology and Demographics==
==Epidemiology and Demographics==
The [[incidence]] is approximately 30 per 100,000 individuals worldwide. Women are more commonly affected with angiomyolipoma than men.
The [[incidence]] of [[angiomyolipoma]] is approximately 30 per 100,000 individuals worldwide. Females are more commonly affected with [[angiomyolipoma]] than males. [[Angiomyolipoma]] commonly affects individuals older than 40 years of age.


==Risk Factors==
==Risk Factors==
[[Tuberous sclerosis]] is a risk factor for the development of [[angiomyolipoma]]. Approximately 50% of individuals with [[tuberous sclerosis]] develop bilateral [[Angiomyolipoma|angiomyolipomas]].
==Screening==
==Screening==
Patients who have [[tuberous sclerosis]] should be screened for angiomyolipoma. Abdominal CT scan is a recommended for screening of angiomyolipoma.<ref name=aaa>Futrelle J. Five Millions by Wireless. Kessinger Publishing; 2004.</ref>
Patients who have [[tuberous sclerosis]] should be screened for [[angiomyolipoma]]. Abdominal [[Computed tomography|CT]] scan is recommended for screening [[angiomyolipoma]]. High fat content is suggestive of [[angiomyolipoma]].


==Natural History, Complications and Prognosis==
==Natural History, Complications and Prognosis==
If left untreated, small angiomyolipomas and those without dilated blood vessels (aneurysms) cause few problems. Small angiomyolipomas are associated with the most favorable prognosis.Common complications of angiomyolipoma include [[infection]], [[hematuria]] and [[flank pain]].
If left untreated, small [[Angiomyolipoma|angiomyolipomas]] and those without dilated [[blood vessels]] ([[Aneurysm|aneurysms]]) cause few symptoms. Small [[Angiomyolipoma|angiomyolipomas]] are associated with the most favorable [[prognosis]]. Common [[complications]] of [[angiomyolipoma]] include [[infection]], [[hemorrhage]], and [[shock]].


==History and Symptoms==
==History and Symptoms==
Symptoms of [[angiomyolipoma]] include [[nausea]], [[vomiting]], and [[abdominal pain]].
[[Symptom|Symptoms]] of [[angiomyolipoma]] include [[fever]], [[nausea]], [[vomiting]], and [[abdominal pain]].


==Physical Examination==
==Physical Examination==
Common physical examination findings of [[angiomyolipoma]] include [[fever]], [[flank]] tenderness, and palpable mass.
Common [[physical examination]] findings of [[angiomyolipoma]] include [[fever]], [[flank]] tenderness, and palpable mass.


==Laboratory Findings==
==Laboratory Findings==
Laboratory findings consistent with the diagnosis of angiomyolipoma include presence of blood cells in urine and elevated white blood cell count.
Laboratory findings consistent with the [[diagnosis]] of [[angiomyolipoma]] include presence of [[red blood cell]]s in [[urine]] and elevated [[white blood cell]] count.


==CT==
==CT==
Abdominal CT scan may be diagnostic for angiomyolipoma. On [[CT scan]], angiomyolipoma is characterized by smooth tumor margin with low intratumoral fat component and homogenous enhancement on both corticomedullary and excretory phase scans.<ref name="pmid14990834">{{cite journal| author=Kim JK, Park SY, Shon JH, Cho KS| title=Angiomyolipoma with minimal fat: differentiation from renal cell carcinoma at biphasic helical CT. | journal=Radiology | year= 2004 | volume= 230 | issue= 3 | pages= 677-84 | pmid=14990834 | doi=10.1148/radiol.2303030003 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=14990834  }} </ref>
[[Abdomen|Abdominal]] [[CT scan]] may be [[diagnostic]] for [[angiomyolipoma]]. On [[CT scan]], [[angiomyolipoma]] is characterized by smooth [[tumor]] margin with low intratumoral fat component and homogenous enhancement on both corticomedullary and excretory phase scans.


==MRI==
==MRI==
Abdominal MRI may be diagnostic of angiomyolipoma. On [[MRI]], angiomyolipoma is cahracterized by high signal intensity on non-fat saturated sequences, and loss of signal following fat saturation.
Abdominal [[Magnetic resonance imaging|MRI]] may be diagnostic of [[angiomyolipoma]]. On [[MRI]], [[angiomyolipoma]] is characterized by high signal intensity on non-[[fat]] saturated sequences and loss of signal following [[fat]] saturation.


==Ultrasound==
==Ultrasound==
On abdominal ultrasound, angiomyolipoma is characterized by hyperechoic lesions, located in the cortex and with posterior acoustic shadowing.
On abdominal [[ultrasound]], [[angiomyolipoma]] is characterized by hyperechoic lesions and [[posterior]] acoustic shadowing in the [[cortex]].


==Other Imaging Studies==
==Other Imaging Studies==
On [[digital subtraction angiography]], angiolipoma is characterized by hypervascular lesions, microvascular aneurysms and absent [[AV shunting]].
On [[digital subtraction angiography]], [[angiolipoma]] is characterized by hypervascular [[lesions]], microvascular [[Aneurysm|aneurysms]] and absent AV shunting.


==Medical Therapy==
==Medical Therapy==
There is no treatment for [[angiomyolipoma]]; the mainstay of therapy is surgical resection or [[embolisation]].
Treatment options include selective [[renal artery]] [[embolization]],nephron sparing [[surgery]]( [[enucleation]] or partial [[nephrectomy]]), complete and radical [[nephrectomy]], radio-frequency [[ablation]] and [[everolimus]]. Treatment and management of the [[Angiomyolipoma]] depends largely on
# Size of the [[tumors]]
#[[Signs]] and [[Symptom|symptoms]]
# Presence or absence of life threatening [[hemorrhage]]
# Its association with the [[tuberous sclerosis]] and
# The presence of the [[Comorbidity|comorbidities]].
 
[[Angiomyolipoma|Angiomyolipomas]] found incidentally,asymptomatic, < 4 cm in size, generally requires no intervention beside periodic evaluation. Medium sized lesion(4-8 cm) should be closely followed with the serial imaging studies(every 6 month and then yearly once stable) and elective intervention provided if the change in the size or symptoms noticed, to increases the chances of renal function salvage. Larger [[lesion]](>8cm), shown to progress to the development of the [[complication]] so treated electively.


==Surgery==
==Surgery==
Surgery is not the first-line treatment option for patients with angiomyolipoma. Transcatheter arterial embolization is usually reserved for patients with complicated disease.<ref name="pmid2864852">{{cite journal| author=Lewis JH, Weingold AB| title=The use of gastrointestinal drugs during pregnancy and lactation. | journal=Am J Gastroenterol | year= 1985 | volume= 80 | issue= 11 | pages= 912-23 | pmid=2864852 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=2864852  }} </ref>
[[Surgery]] is not the first-line treatment option for patients with [[angiomyolipoma]]. Transcatheter [[Artery|arterial]] [[embolization]] is usually reserved for patients with complicated disease.


==References==
==References==
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2], Faizan Sheraz, M.D. [3], Rekha, M.D.

Overview

Angiomyolipoma is a benign renal neoplasm previously considered to be a hamartoma or choristoma, but now known to be neoplastic. It is composed of variable amounts of fat, vascular, and smooth muscle elements. The fat density of the tumor on CT scan has been regarded to be pathognomonic. The lesion is well demarcated and contains mature elements. It occurs in more than 50% of individuals with tuberous sclerosis, often bilaterally. On gross pathology, well circumscribed and uniform yellow mass is characteristic finding of angiomyolipoma. Angiomyolipoma is caused by a defect in the TSC1 gene. Angiomyolipoma must be differentiated from retroperitoneal liposarcoma, adrenal myelolipoma, and renal cell carcinoma. If left untreated, small angiomyolipomas and those without dilated blood vessels (aneurysms) cause few symptoms. Small angiomyolipomas are associated with the most favorable prognosis. Common complications of angiomyolipoma include infection, hematuria and hemorrhage. Abdominal CT scan may be diagnostic for angiomyolipoma. On CT scan, angiomyolipoma is characterized by smooth tumor margin with low intratumoral fat component and homogenous enhancement on both corticomedullary and excretory phase scans. Surgery is not the first-line treatment option for patients with angiomyolipoma. Transcatheter arterial embolization is usually reserved for patients with complicated disease.

Historical Perspective

Angiomyolipoma was first described as a tumor in 1911 by Fisher. He also noted and described its association with the Tuberous Sclerosis. It has been named as Angiomyolipoma by Morgan and associates in 1951.

Classification

Angiomyolipoma may be classified according to radiologic appearance into 7 subtypes: classic angiomyolipoma, triphasic angiomyolipoma, fat poor angiomyolipoma, hyperattenuating angiomyolipoma, isoattenuating angiomyolipoma, angiomyolipoma with epithelial cysts, and angiomyolipoma in lymphangioleiomyomatosis.

Pathophysiology

On gross pathology, well circumscribed and uniform yellow mass is characteristic finding of angiomyolipoma. The components of an angiomyolipoma include vascular cells, immature smooth muscle cells and fat cells. Angiomyolipoma is caused by a defect in TSC1 gene. Diseases associated with angiomyolipoma include von Hippel-Lindau syndrome and tuberous sclerosis. Cytologic features of angiomyolipoma include round nuclei and bland chromatin. Immunohistochemistry markers of angiomyolipoma include positive melanocytic markers.

Causes

Angiomyolipoma is caused by a mutation in the TSC1 gene. It can also be caused by a defect in TSC2 gene.

Differentiating Angiomyolipoma from other Diseases

Angiomyolipoma must be differentiated from retroperitoneal liposarcoma, adrenal myelolipoma, and renal cell carcinoma.

Epidemiology and Demographics

The incidence of angiomyolipoma is approximately 30 per 100,000 individuals worldwide. Females are more commonly affected with angiomyolipoma than males. Angiomyolipoma commonly affects individuals older than 40 years of age.

Risk Factors

Tuberous sclerosis is a risk factor for the development of angiomyolipoma. Approximately 50% of individuals with tuberous sclerosis develop bilateral angiomyolipomas.

Screening

Patients who have tuberous sclerosis should be screened for angiomyolipoma. Abdominal CT scan is recommended for screening angiomyolipoma. High fat content is suggestive of angiomyolipoma.

Natural History, Complications and Prognosis

If left untreated, small angiomyolipomas and those without dilated blood vessels (aneurysms) cause few symptoms. Small angiomyolipomas are associated with the most favorable prognosis. Common complications of angiomyolipoma include infection, hemorrhage, and shock.

History and Symptoms

Symptoms of angiomyolipoma include fever, nausea, vomiting, and abdominal pain.

Physical Examination

Common physical examination findings of angiomyolipoma include fever, flank tenderness, and palpable mass.

Laboratory Findings

Laboratory findings consistent with the diagnosis of angiomyolipoma include presence of red blood cells in urine and elevated white blood cell count.

CT

Abdominal CT scan may be diagnostic for angiomyolipoma. On CT scan, angiomyolipoma is characterized by smooth tumor margin with low intratumoral fat component and homogenous enhancement on both corticomedullary and excretory phase scans.

MRI

Abdominal MRI may be diagnostic of angiomyolipoma. On MRI, angiomyolipoma is characterized by high signal intensity on non-fat saturated sequences and loss of signal following fat saturation.

Ultrasound

On abdominal ultrasound, angiomyolipoma is characterized by hyperechoic lesions and posterior acoustic shadowing in the cortex.

Other Imaging Studies

On digital subtraction angiography, angiolipoma is characterized by hypervascular lesions, microvascular aneurysms and absent AV shunting.

Medical Therapy

Treatment options include selective renal artery embolization,nephron sparing surgery( enucleation or partial nephrectomy), complete and radical nephrectomy, radio-frequency ablation and everolimus. Treatment and management of the Angiomyolipoma depends largely on

  1. Size of the tumors
  2. Signs and symptoms
  3. Presence or absence of life threatening hemorrhage
  4. Its association with the tuberous sclerosis and
  5. The presence of the comorbidities.

Angiomyolipomas found incidentally,asymptomatic, < 4 cm in size, generally requires no intervention beside periodic evaluation. Medium sized lesion(4-8 cm) should be closely followed with the serial imaging studies(every 6 month and then yearly once stable) and elective intervention provided if the change in the size or symptoms noticed, to increases the chances of renal function salvage. Larger lesion(>8cm), shown to progress to the development of the complication so treated electively.

Surgery

Surgery is not the first-line treatment option for patients with angiomyolipoma. Transcatheter arterial embolization is usually reserved for patients with complicated disease.

References


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