Logan Steele
Angiomyolipomas are benign tumours that form in the kidneys and, less commonly, in the liver and pancreas. They are composed of blood vessels, smooth muscle cells, and fat cells. While angiomyolipomas are typically benign, they can cause serious complications if they grow too large, including bleeding, anemia, fever, and kidney pain. In rare cases, angiomyolipomas have been found to contain striated granules, which are typically found in melanosomes. However, it is unclear if these granules contain striated muscle.
| Characteristics | Values |
|---|---|
| Composition | Fat (adipose tissue), smooth muscle, and blood vessels |
| Types | Monophasic AMLs, Epithelioid angiomyolipomas, Classic (triphasic) AMLs |
| Treatment | Arterial embolization, nephrectomy, surgery, embolisation, drug therapy |
| Symptoms | Bleeding, anemia, fever, kidney pain, high blood pressure |
| Occurrence | Rare in the liver, kidney, pancreas, and other organs |
| Structure | Perivascular epithelioid cells (PEC), sarcomeres, myosin-rich dark anisotropic (A) band, actin-dominated light isotropic (I) bands |
| Diagnosis | Ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), immunohistochemistry |
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What You'll Learn
- Angiomyolipomas are benign tumours that can form in the kidney, liver or pancreas
- They are composed of blood vessels, smooth muscle and fat cells
- The tumours are treated with surgery or arterial embolization if they grow too large
- Angiomyolipomas are associated with the genetic disease tuberous sclerosis
- They are very rare in the liver, with only 25 cases reported in English literature
Angiomyolipomas are benign tumours that can form in the kidney, liver or pancreas
Angiomyolipomas are benign tumours that can form in the kidney, liver, or pancreas. They are composed of varying proportions of vascular cells, immature smooth muscle cells, and fat cells. Angiomyolipomas are derived from unique cells called perivascular epithelioid cells, which are found surrounding blood vessels and resemble epithelial cells. These tumours are typically well-circumscribed and can be categorised into three types:
- Classic (triphasic) AMLs: These are the most common type, containing three types of tissue—blood vessels, fat, and smooth muscle tissue.
- Monophasic AMLs: These tumours contain almost all of one type of tissue, such as smooth muscle or fat.
- Epithelioid angiomyolipomas: These are mostly made up of cells that line the kidney's blood vessels (epithelioid cells) and may be more likely to become cancerous.
The diagnosis of angiomyolipoma is established by demonstrating the presence of macroscopic fat within the lesion, as other renal masses may also show similar signal characteristics on imaging. Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) are the three methods used to detect angiomyolipomas. Treatment options depend on factors such as the tumour's size, symptoms, and potential complications. If the tumour is less than 4 cm in diameter and isn't causing any symptoms, regular imaging surveillance is recommended. For larger tumours, treatment options include embolisation, ablation surgery (lumpectomy, partial or total nephrectomy), and drug therapy, which is currently in the research stage.
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They are composed of blood vessels, smooth muscle and fat cells
Angiomyolipomas are benign tumours that form in the kidney, although they can also be found in the liver and, less commonly, the ovary, fallopian tube, spermatic cord, palate, and colon. They are composed of blood vessels, smooth muscle, and fat cells, with the amount of each varying between tumours. The gross appearance of the tumour varies with the predominant component. For example, tumours with significant fat content tend to be soft and yellow, whereas tumours with mostly smooth muscle content are firm, with a tan-white cut surface.
The classic form of angiomyolipoma contains three types of tissue: blood vessels, fat, and smooth muscle tissue. However, some tumours contain almost all of one type of tissue, such as smooth muscle or fat. Angiomyolipomas are typically benign, but they can grow to the point of impairing kidney function or causing blood vessels to dilate and burst, leading to bleeding. This risk of rupture with bleeding or secondary damage/destruction of surrounding structures is proportional to the size of the lesion. If the tumour grows larger than about 4 cm, it could cause bleeding (haemorrhage), which can be life-threatening if left untreated.
Angiomyolipomas are derived from unique cells designated as perivascular epithelioid cells, which are found surrounding blood vessels and resemble epithelial cells. These cells are typically clustered around blood vessels and are large, with abundant clear or acidophilic cytoplasm and a round vacuolated nucleus often exhibiting a nucleolus. They are believed to have derived from a common progenitor cell that developed a "second-hit" mutation.
Angiomyolipomas are treated with embolisation, which involves blocking blood flow to the tumour to shrink it and reduce the risk of bleeding. They can also be treated with surgery, either by removing the entire kidney containing the tumour or just the part of the kidney containing it.
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The tumours are treated with surgery or arterial embolization if they grow too large
Angiomyolipomas are benign tumours composed of smooth muscle cells, thick-walled vessels, and adipose cells. They are usually treated with resection. However, if they grow too large, they may require surgery or arterial embolization to prevent them from causing symptoms such as bleeding, anaemia, fever, and kidney pain.
Arterial embolization is a procedure that blocks blood flow to the tumour, causing it to shrink and reduce the risk of bleeding. During the procedure, a small incision is made in the inner thigh, and a thin tube (catheter) is inserted. Tiny beads are then injected through the catheter into the artery to plug it up and block blood flow to the tumour. This procedure can be performed prior to surgical resection to reduce blood loss during surgery and make it easier to remove the tumour.
In the case of angiomyolipomas, arterial embolization can be used to shrink the tumour and reduce the risk of bleeding. It is often considered for tumours larger than 4 centimetres, as they can pose a risk of bleeding.
Surgery is another option for treating large angiomyolipomas. There are two types of surgical procedures that can be performed: partial nephrectomy and complete nephrectomy. During a partial nephrectomy, only the portion of the kidney containing the angiomyolipoma is removed, while a complete nephrectomy involves removing the entire kidney.
It is important to note that kidney failure can occur after treatment or surgery for kidney conditions. Therefore, healthcare providers will discuss the risks and develop a care plan to manage symptoms and ensure the best possible outcome for the patient.
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Angiomyolipomas are associated with the genetic disease tuberous sclerosis
Angiomyolipomas are benign tumours composed of varying amounts of fat, smooth muscle, and vascular tissue. They are most commonly found in the kidney, but can also occur in the liver. While angiomyolipomas are generally sporadic, they are strongly associated with the genetic disease tuberous sclerosis complex (TSC).
TSC is a rare autosomal dominant disease that affects approximately 1–2 million individuals worldwide. It is caused by mutations in either the hamartin gene (TSC1) or the tuberin gene (TSC2), leading to the growth of nonmalignant hamartomas in various organs, including the kidney, brain, lung, skin, and heart. The clinical manifestations of TSC are diverse and can affect virtually any organ in the body.
The association between angiomyolipomas and TSC is well-established. It is estimated that up to 80% of patients with TSC will develop at least one angiomyolipoma in their lifetime. In children with TSC, the growth of angiomyolipomas can be rapid and unpredictable. The median age at first angiomyolipoma detection in this population is 11 years, with a range of 2 to 26 years.
Angiomyolipomas associated with TSC have distinct characteristics compared to sporadic cases. They tend to be larger, grow faster, and are at a higher risk of bleeding. Additionally, TSC-associated angiomyolipomas often develop multiple bilateral lesions, resulting in a significant tumour burden on the kidneys. The treatment and management of angiomyolipomas in TSC patients may differ from sporadic cases due to these unique characteristics.
The diagnosis of angiomyolipomas in TSC patients is typically based on imaging techniques such as computed tomography or magnetic resonance imaging, which assess the fat content within the lesion. Treatment options may include arterial embolization, partial nephrectomy, or robotic partial nephrectomy. Yearly renal ultrasounds and magnetic resonance imaging are recommended for all patients with TSC to monitor for angiomyolipoma growth and facilitate early intervention if needed.
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They are very rare in the liver, with only 25 cases reported in English literature
Angiomyolipomas are benign tumours composed of smooth muscle cells, thick-walled vessels, and adipose cells. They are rare in the liver, with only 25 cases reported in English literature. However, they are the most common benign kidney tumour and are especially prevalent in people with tuberous sclerosis complex (TSC). Angiomyolipomas can be challenging to diagnose, as the fat cell component may be inconspicuous, and they can vary in appearance depending on their predominant tissue type.
Hepatic angiomyolipomas often contain hematopoietic elements, including megakaryocytes and erythroid and myeloid precursors. They can be subcategorized as lipomatous, myomatous, or angiomatous, depending on whether fat, muscle, or vascular tissue is most prominent. The relative amounts of these tissues determine the MR imaging appearance of the tumour.
The rarity of hepatic angiomyolipomas may be due to the unique cells from which they arise. Angiomyolipomas are derived from perivascular epithelioid cells (PECs), which were first identified in 1991 through immunohistochemical and ultrastructural investigations of renal and hepatic angiomyolipomas. These PECs are typically clustered around blood vessels and exhibit immunoreactivity for HMB-45, a marker previously associated with melanocytic tumours.
Several studies have reported cases of hepatic angiomyolipomas. One study described two additional cases, one of which was multicentric, and the tumour cells contained numerous electron-dense granules with transverse striations. Another study reported eight cases, while others have reported five, six, and twelve cases. These studies contribute to the limited body of literature on hepatic angiomyolipomas, highlighting their rarity and distinct characteristics.
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Frequently asked questions
Angiomyolipomas are benign tumours composed of blood vessels, smooth muscle cells, and fat cells. They are most commonly found in the kidney but can also occur in the liver and pancreas.
Many people with angiomyolipomas do not experience any symptoms. However, if the tumour grows too large, it may cause bleeding, anemia, fever, kidney pain, and high blood pressure.
Small angiomyolipomas usually do not require treatment. Larger angiomyolipomas can be treated with embolisation or surgery to reduce the risk of bleeding.
No, angiomyolipomas are typically benign tumours. However, epithelioid angiomyolipomas, which are mostly made up of cells lining the kidney's blood vessels, may have a higher risk of becoming cancerous.
Angiomyolipomas contain smooth muscle, not striated muscle. Striated muscles, such as skeletal and cardiac muscles, have a highly ordered ultrastructure consisting of sarcomeres, which are basic contractile units.
