RENAL ANGIOMYOLIPOMA

OVERVIEW

•  The most frequent benign kidney tumors are renal angiomyolipomas (AMLs). 
• They are often highly vascular, predominantly made up of smooth muscles and fatty tissues, and characterized by perivascular epithelioid differentiation.
• The majority of tumors are discovered by chance during radiological imaging
•  They have typical signs and symptoms, including severe retroperitoneal bleeding, flank discomfort, and extensive hematuria.
• A significant amount of adipose tissue must be shown on radiological imaging as the primary diagnostic indicator of classic angiomyolipoma.
• Although harmless, the tumors may invade the lymphatics, perirenal fat, renal sinus, and other neighboring organs. 
• Angiomyolipomas are typically managed based on their clinical symptoms, number, size, growth, and malignant potential. For instance, epithelial angiomyolipoma of the kidney is a rare subtype of angiomyolipoma that has the potential to be cancerous.
• Angiomyolipomas develop when the mTOR pathway is unchecked.  

ETIOLOGY

• The majority of renal angiomyolipomas (80%) are unknown; 20% are “hereditary” diseases due to mutations in the TSC1 or TSC2 genes
• However, the specific reason for this cause is unknown.
• Hereditary angiomyolipomas are more likely to be larger, earlier in occurrence, bilateral, and multicentric, and can grow more quickly, bleed, and progress to malignancy.
• Moreover, angiomyolipomas are more frequent in patients with particular medical disorders, such as: Lymphangioleiomyomatosis (LAM) and complex tuberous sclerosis (TSC)

• The development of benign tumors is a symptom of the rare, familial, autosomal dominant genetic condition known as tuberous sclerosis. It is also linked to epilepsy,  adenoma, and mental impairments. 

EPIDEMIOLOGY

• Although it is believed that tuberous sclerosis is underdiagnosed, the total incidence is estimated to be 1 per 10,000 people.
•  Angiomyolipomas will form in more than 50% of people with tuberous sclerosis.
• Almost 80% of single and sporadic cases make up the total prevalence rate for renal angiomyolipomas, which varies from 0.13 to 2.2%. 
• The remaining twenty percent appear in conjunction with tuberous sclerosis complex or pulmonary lymphangioleiomyomatosis.
• Renal angiomyolipomas seem to affect more females than males. Females typically have larger tumors than males, as well. Angiomyolipomas grow more quickly in pregnant women. Angiomyolipoma hemorrhage appears to be more likely when receiving exogenous estrogen medication. 
• The majority of angiomyolipomas are benign, and they very rarely turn cancerous. Angiomyolipomas are typically asymptomatic and tend to stabilize in size. Just 9% of people eventually get more extensive.
• The likelihood that a tumor will develop, proliferate, bleed, and cause symptoms increases with tumor size (>6 cm). 

TYPES OF ANGIOMYOLIPOMA 

Based on cells and tissues, there are three types 

Classic (triphasic) AMLs: consist of fat, smooth muscle, and blood vessels.

monophasic AMLs: composed of any one type of tissue, such as fat or smooth muscle, 

Epithelioid angiomyolipomas: The majority of the cells in these angiomyolipomas line the blood vessels in your kidneys (epithelioid cells). There may be an increased risk of cancer from certain tumors.

SIGNS AND SYMPTOMS

40% of kidney angiomyolipomas greater than 4 cm were symptomatic, according to the 4 cm size criterion. 

• Abdominal or flank pain
• Hematuria
• Palpable mass or masses
• Hypertension
• Flank tenderness
• Nausea and vomiting
• fatigue and weakness.
• Urinary tract infections 
• Fever
• Severe renal insufficiency
• shock

INVESTIGATIONS 

• Diagnostic imaging is the key to detecting renal angiomyolipoma. 
• Angiomyolipomas are typically not diagnosed with a biopsy; however, in challenging or complex instances, such as renal mass lesions that are fat-invisible, a biopsy may be required to rule out malignancy. 
• The below-mentioned imaging techniques can be used to diagnose this condition

Computed tomography

Magnetic resonance imaging

Percutaneous biopsy 

Renal nuclear scanning

Ultrasonography

• If the ultrasound reveals a substantial increase (>2.5 mm/year) or a highly hazardous alteration, a CT scan or MRI is advised. 
• CT scans are beneficial for patients because of increased accessibility and decreased cost 
• To make the comparison more accurate, it is useful to employ the same imaging modality that was used to make the initial diagnosis. For these reasons, if one hasn’t been done already, a baseline ultrasound is recommended for newly diagnosed angiomyolipomas. 
• When there is a need to distinguish tumors from angiomyolipomas, accuracy is increased by combining tumor grade with ultrasound image-based statistical textural analysis.
• In fat-poor lesions, MRI is thought to be superior.
• The primary purpose of percutaneous renal biopsies is to distinguish benign masses from malignant renal diseases. 
•  Biopsies are typically not advised until the majority of renal masses exhibit revealing symptoms of cancer, and benign lesions, like angiomyolipomas, are typically correctly detected using imaging.
•  Necrosis, intralesional calcifications, or lymphadenopathy are frequently present in lesions that raise the possibility of malignancy; in these circumstances, it is advisable to perform surgical excision immediately.
• When other imaging modalities are unclear, it may also help distinguish between renal and pseudo masses. Renal nuclear scanning using technetium-99m (Tc) MAG3 renography

TREATMENT & MANAGEMENT

Most angiomyolipoma patients are asymptomatic and don’t need treatment; only minor patients recommend treatment.

Treatment is advised for the following conditions:

Tumor-related symptoms such as persistent pain and massive lesions (now >4 cm, >6 cm)

multiple lesions, Lesions that are growing more than 2.5 mm each year, > 5 mm-sized intralesional aneurysms, inadequate access to follow-up or emergency healthcare, patient non-compliance, women of reproductive age presenting with tumors, High-risk professions women receiving hormonal therapy

• medical treatments include the use of mTOR inhibitors 
• Surgical interventions include selective renal artery embolization, thermal ablation (laser therapy and cryotherapy), and surgical excision( complete nephrectomy, partial nephron-sparing surgery).

The side effects associated with drug usage are unavoidable

• Close monitoring of the tumors through the use of imaging modalities twice a year (potentially advancing) or once a year (small,slow-growing) 
• Treatment is usually not recommended for the majority of angiomyolipomas.
• Treatment is necessary when there are current symptoms, size (>6 cm), growth (>2.5 mm/yr), intratumoral aneurysms (>5 mm), high-risk circumstances, and access issues to healthcare.
•  Adopting the least intrusive treatment approach is best if it is available.
• While treating hereditary angiomyolipomas, the drug Everolimus (10 mg) has been effective at slowing tumor growth and accelerating tumor shrinkage. 
• Everolimus usage in the sporadic type of Angiomyolipoma is not clear.
• Thermal treatments are efficient for both benign and malignant tumors. 
• The interventional radiologist’s participation is critical to the diagnosis of the disease. 

PROGNOSIS

Small angiomyolipomas with no aneurysms have a better prognosis than the larger ones with aneurysms of >5mm 

COMPLICATIONS 

• Bleeding and renal impairment, infections, and scars are complications from Angiomyolipoma 
• Complicated findings in computed tomography reveal the compression of the pyelocalyceal system in three cases, intratumoral bleeding in two cases, a rupture leading to subcapsular, perirenal, or pararenal hematoma, extensive intrarenal/parapelvic hematoma, and cystic degeneration 

CONCLUSION

A multidisciplinary approach is highly suggested in angiomyolipoma conditions (nephrologist, pathologist, radiologist, Oncologist, Urologist, Clinical pathologist, general surgeon, etc.).

Providing patient education sessions or videos can better explain the patient’s condition

Mental and physical support for patients is highly recommended

Consulting and following up with the doctor regularly is beneficial to the individual.

The goal of all medical interventions should be to maintain renal function while halting the progression of the illness and its consequences.

FREQUENTLY ASKED QUESTIONS