of an Angiomyolipoma (vascular cells, immature smooth muscle cells, and fat cells) contain a "second-hit" mutation, they are believed to have derived from a common progenitor cell that developed the common second-hit mutation. Diagnosis Three methods of scanning can detect Angiomyolipomas: ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI). Ultrasound is standard and is particularly sensitive to the fat in Angiomyolipomas, but less so to the solid components. However, accurate measurements are hard to make with ultrasound, particularly if the Angiomyolipoma is near the surface of the kidney (grade III). CT is very detailed and fast, and allows accurate measurement. However, it exposes the patient to radiation and the dangers that a contrast dye used to aid the scanning may itself harm the kidneys. MRI is safer than CT, but many patients (particularly those with the learning difficulties or behavioural problems found in tuberous sclerosis) require sedation or general anaesthesia, and the scan cannot be performed quickly. Some other kidney tumours contain fat, so the presence of fat is not diagnostic. Distinguishing a fat-poor angiomyolipoma from a renal cell carcinoma (RCC) can be difficult. Both minimal fat AMLs and 80% of the clear-cell type of RCCs display signal drop on an out-of-phase MRI sequence compared to in-phase. Thus, a lesion growing at greater than 5 mm per year may warrant a biopsy for diagnosis. Incidental discovery of angiomyolipomas (AML) should trigger consideration of tuberous sclerosis complex (TSC), especially those who aged 18 to 40 years, and those with bilateral angiomyolipomas. Those with AML and TSC has 20 to 50% chance of having haemorrhage from AML, and of those having haemorrhages, 20% of them have life-threatening haemorrhages. Screening for TSC includes a detailed physical exam, including dermatologic and ophthalmologic evaluations, by TSC expert clinicians and a CT or MRI of the brain. Screening for LAM includes a high-resolution CT of the lung and pulmonary function testing. Treatment Everolimus is FDA approved for the treatment of Angiomyolipomas. Treatment should be considered for asymptomatic, growing AMLs measuring larger than 3 cm in diameter. Angiomyolipomas do not normally require surgery unless life-threatening bleeding is present. Some centers may perform preventative selective embolisation of the Angiomyolipoma if it is more than 4 cm in diameter, due to the risk of hemorrhage. People with Tuberous Sclerosis are advised to have yearly renal scans, though patients with very stable lesions could be monitored less frequently. The