What are the other Names for this Condition? (Also known as/Synonyms)

• Subgaleal AML

What is Subgaleal Angiomyolipoma? (Definition/Background Information)

• An angiomyolipoma (AML) is a benign tumor that is a mixture of blood vessels (angio-), smooth muscles (myo-), and fat (or lipoma). The tumor is seen among a wide age range of adults and can occur at various locations in the body. The most common location is the kidney (renal AML)
• Subgaleal Angiomyolipoma is a very uncommon extrarenal AML that may be present in adult men and women. Subgaleal refers to the space in between the scalp (specifically the scalp galea aponeurosis) and the skull
• Angiomyolipoma can be associated with a syndrome (tuberous sclerosis) in some cases, termed syndromic angiomyolipoma. In a majority of cases, it may not be associated with a genetic disorder, in which it is termed non-syndromic angiomyolipoma. Subgaleal Angiomyolipoma may be associated with tuberous sclerosis
• The signs and symptoms depend upon the size and location of the tumors. Large tumors may cause the presence of mass on the scalp, headaches, and neurological symptoms, if the brain is involved
• Typically, a surgical excision and removal of Subgaleal Angiomyolipoma may be undertaken. The prognosis is generally excellent on its complete removal since it is a benign tumor
• However, the prognosis also depends upon a set of factors that includes the severity of the signs and symptoms, age and overall health of the individual, response to treatment, and its association with tuberous sclerosis

Who gets Subgaleal Angiomyolipoma? (Age and Sex Distribution)

No specific demographics for Subgaleal Angiomyolipoma are evident, since it is an extremely rare tumor. On examination of the cases, the tumor is seen to affect adult men and women, with a female preponderance.

The demographics for angiomyolipoma, in general, is as follows:

• Sporadic (non-syndromic) cases of angiomyolipoma are usually seen in the age group 45-55 years
• When in association with tuberous sclerosis complex (syndromic cases), the age group in which the tumor is often manifested is between 25-35 years
• No ethnic or racial preference is seen

What are the Risk Factors for Subgaleal Angiomyolipoma? (Predisposing Factors)

Currently, no specific risk factors have been noted for Subgaleal Angiomyolipoma. The risk factors for angiomyolipoma, in general, may include the following:

• Tuberous sclerosis (TS) is a risk factor for angiomyolipoma, and hence, a family history of TS can increase the risk. Tuberous sclerosis complex is an inherited genetic disorder that can cause the formation of other tumor types, such as astrocytomas, rhabdomyomas, phakomas, oncocytomas, and angiofibromas, at various body locations
• In general, AML can also be associated with other syndromes/disorders including:
  • von Recklinghausen disease (neurofibromatosis type I)
  • von Hippel-Lindau disease
  • Sturge-Weber syndrome
  • Autosomal dominant polycystic kidney disease
• Some reports indicate that events causing an hormonal imbalance in the body, such as puberty and pregnancy in women, may be a risk factor

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Subgaleal Angiomyolipoma? (Etiology)

The exact cause and mechanism of Subgaleal Angiomyolipoma formation, in a majority of cases, is unknown. Solitary tumors are believed to be the result of sporadic mutations on TSC1 or TSC2 genes, implying that they do not have a preceding family history of the condition.

• Research has shown that the tumors arise from cells called perivascular epithelioid cells (PEC), which surrounds the blood vessels. Hence, angiomyolipoma (AML) is a type of a tumor known as a PEComa
• Multiple angiomyolipomas are known to occur in a background of tuberous sclerosis (TS), which is a genetic condition. It may also occur when there is a positive family history of the condition
• Tuberous sclerosis complex is caused by genetic alterations involving the TSC1 and TSC2 gene. In non-TS associated AML, the loss of heterozygosity on TSC1/TSC2 gene has been noted. Also, some reports indicate that mutations on RHEB gene are observed in sporadic (non-syndromic) cases
• In general, syndromic AML is also associated with other genetic disorders such as von Recklinghausen disease, von Hippel-Lindau disease, Sturge-Weber syndrome, and autosomal dominant polycystic kidney disease
• Some research indicates that hormonal influence may play a role in AML formation for the following reasons:
  • The tumor is more often seen in women
  • It grows larger during pregnancy
  • The onset can be after puberty
  • High progesterone receptor activity is present on microscopic examination

What are the Signs and Symptoms of Subgaleal Angiomyolipoma?

The signs and symptoms of Subgaleal Angiomyolipoma may include the following:

• Most tumors are small-sized and may not exhibit any signs and symptoms
• Large tumors (size over 4 cm) can compress the surrounding structures or form a prominent bulge
• Tumors tend to grow larger in size during pregnancy
• Headaches
• Nausea and vomiting
• Disproportionate head size
• Bleeding can occur within large tumors; subgaleal hemorrhage within the tumors can lead to tissue death (or infarction)
• Subgaleal hematoma due to bleeding from the tumor can spread to other parts of the face
• Blood accumulation can occur around the eye, resulting in ‘raccoon eyes’

In general, the following may be observed about angiomyolipoma:

• In sporadic cases (when not associated with tuberous sclerosis), angiomyolipoma is usually single. Often with sporadic tumors, they tend to be larger and so pain may be observed
• With tuberous sclerosis (TS), multiple tumors may be seen around the body or in the same organ. But with TS, tumors are known to be more asymptomatic and are often discovered incidentally

How is Subgaleal Angiomyolipoma Diagnosed?

A diagnosis of Subgaleal Angiomyolipoma may involve the following tests and procedures:

• Complete physical (oral) exam with evaluation of medical history
• Plain X-ray of the skull
• CT or CAT scan with contrast of the head and neck may show a well-defined mass, which may have calcifications. This radiological procedure creates detailed 3-dimensional images of structures inside the body
• MRI scans of the brain: Magnetic resonance imaging (MRI) uses a magnetic field to create high-quality pictures of certain parts of the body, such as tissues, muscles, nerves, and bones. These high-quality pictures may reveal the presence of the tumor
• Vascular angiographic studies of the tumor

Although the above modalities can be used to make an initial diagnosis, a tissue biopsy of the tumor is necessary to make a definitive diagnosis to begin treatment. The tissue for diagnosis can be procured in multiple different ways which include:

• Fine needle aspiration (FNA) biopsy of the tumor: A FNA biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a FNA biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy is preferred
• Core biopsy of the tumor
• Open biopsy of the tumor

Tissue biopsy:

• A tissue biopsy of the tumor is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis
• Biopsy specimens are studied initially using Hematoxylin and Eosin staining. The pathologist then decides on additional studies depending on the clinical situation
• The tumors may have varying proportions of blood vessels, smooth muscle, and fat cells, when examined by a pathologist under a microscope
• Sometimes, the pathologist may perform special studies, which may include immunohistochemical stains, molecular testing, and very rarely, electron microscopic studies to assist in the diagnosis

Note: A differential diagnosis, to eliminate other tumor types is considered, before arriving at a conclusion.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Subgaleal Angiomyolipoma?

The complications of Subgaleal Angiomyolipoma are dependent upon the size of the tumor and may include:

• Large tumor masses may get secondarily infected with bacteria or fungus
• Stress and anxiety due to fear of brain cancer
• Damage to the muscles, vital nerves, and blood vessels, during surgery
• Post-surgical infection at the wound site is a potential complication
• Research has not conclusively proven that angiomyolipoma can turn malignant. Some cases of sarcoma developing from AML (not associated with tuberous sclerosis) have been noted

How is Subgaleal Angiomyolipoma Treated?

The treatment measures for Subgaleal Angiomyolipoma may include the following:

• Majority of asymptomatic tumors are not surgically removed: The healthcare provider may recommend a ‘wait and watch’ approach for small-sized tumors presenting mild signs and symptoms, after a diagnosis of angiomyolipoma is established
• Pain medications for AML causing pain
• Surgical intervention with complete excision can result in a complete cure. It can also help reduce the chances of tumor recurrence
• Tumor embolization is a possible treatment option. Here the blood supply to the tumor is blocked resulting in its shrinkage or death
• The FDA-approved medication FYARRO (sirolimus protein-bound particles for injectable suspension) may be used for the rare malignant PEComas
• Treatment of the underlying or associated conditions, if any
• Post-operative care is important until the surgical wound heals
• Follow-up care with regular screening may be recommended by the healthcare provider

How can Subgaleal Angiomyolipoma be Prevented?

Current medical research has not established a method of preventing both syndromic and non-syndromic forms of Subgaleal Angiomyolipoma. However, in case it is associated with genetic disorders, such as tuberous sclerosis, then the following may be considered:

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as tuberous sclerosis
• Regular medical screening at periodic intervals with tests and physical examinations are strongly recommended

What is the Prognosis of Subgaleal Angiomyolipoma? (Outcomes/Resolutions)

• The prognosis of Subgaleal Angiomyolipoma depends upon the severity of the signs and symptoms. It also depends upon the overall health of the individual, association with tuberous sclerosis or other genetic conditions, and response to therapy
• Typically, individuals with small-sized tumors have a better prognosis than those with larger-sized tumors (over 4 cm in size). Also, those with non-syndromic (sporadic) tumors have a comparatively better prognosis than individuals with tumors that are seen in association with a genetic disorder (syndromic)
• In most cases, the prognosis of small-sized solitary tumors is excellent with surgical intervention or appropriate treatment, since these are benign tumors

Additional and Relevant Useful Information for Subgaleal Angiomyolipoma:

Angiomyolipoma can occur at various locations in the body, such as the soft tissue, skin, uterus, fallopian tube, spermatic cord, penis, liver, and lung.