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Renal angiomyolipomas (AMLs): Epidemiology, pathogenesis, clinical manifestations, and diagnosis

Renal angiomyolipomas (AMLs): Epidemiology, pathogenesis, clinical manifestations, and diagnosis
Literature review current through: Jan 2024.
This topic last updated: Nov 10, 2023.

INTRODUCTION — Angiomyolipomas (AMLs) are neoplasms occurring in the kidney that are composed of varying amounts of tissues resembling blood vessels, smooth muscle, and adipose. The vast majority of AMLs are benign but malignant AMLs have been reported [1-4].

Renal AMLs may either occur sporadically or in association with either tuberous sclerosis complex (TSC), sporadic lymphangioleiomyomatosis (LAM), or a combination (TSC-LAM).

This topic will discuss the epidemiology, pathogenesis, clinical manifestations, and diagnosis of renal AMLs. Other related issues are discussed elsewhere:

Management and prognosis of renal AMLs (see "Renal angiomyolipomas (AMLs): Management")

Kidney manifestations of TSC (see "Renal manifestations of tuberous sclerosis complex")

Renal AMLs associated with LAM (see "Sporadic lymphangioleiomyomatosis: Clinical presentation and diagnostic evaluation", section on 'Renal angiomyolipomas')

A general overview of TSC-LAM (see "Tuberous sclerosis complex associated lymphangioleiomyomatosis in adults")

An evaluation of incidental lesions of the kidney (see "Evaluation of the incidental kidney lesion")

EPIDEMIOLOGY — AMLs have been reported in 0.13 to 2.2 percent of asymptomatic adults who underwent imaging [5,6]. In a population-based study of approximately 18,000 asymptomatic adults who underwent kidney ultrasound, renal AMLs were identified in 24 patients (0.13 percent) [5]. In another study of approximately 2000 potential kidney donors who underwent computed tomography (CT) scans, renal AMLs were identified in 43 patients (2.2 percent) [6].

Renal AMLs appear to be more common among females [7]. In a study of over 2000 patients with tuberous sclerosis complex (TSC), 58 percent of the 1070 patients with AML(s) were female [8]. In smaller studies that included few or no individuals with TSC, 78 to 82 percent of patients with AML were female [9,10]. This female predominance may be related to the role of estrogen in fostering the growth of AMLs. (See 'Additional pathogenetic mechanisms in females' below.)

The majority of AMLs (over 80 percent) are sporadic. The remainder are mostly associated with TSC; sporadic lymphangioleiomyomatosis (LAM), or a combination of LAM and TSC (TSC-LAM) likely account for a small minority of cases [7]. In one study of patients with sporadic AMLs, approximately 5 percent of patients (all female) had four or more cysts on their chest CT, which suggested the possibility of undiagnosed LAM [10]. However, a confirmation of the diagnosis of LAM was not part of the study methods.

The prevalence of renal AMLs is markedly higher among patients with TSC [8,11-13], and this prevalence increases with age [7,11,12,14-20]. In an international, multicenter registry study (Tuberous Sclerosis registry to increase disease Awareness [TOSCA]), approximately one-half (52 percent) of over 2000 patients (age range 0 to 71 years) were found to have renal AMLs [8]. Compared with patients who had a TSC1 mutation, those who had a TSC2 mutation were more likely to have a renal AML (59 versus 33 percent), have the AML identified at a younger age (13 versus 24 years), have an AML with a size >3 cm (32 versus 12 percent), and have an AML that grew in size over time (24 versus 12 percent). (See "Renal manifestations of tuberous sclerosis complex", section on 'Genetics'.)

The prevalence of renal AMLs in patients with sporadic LAM is also higher compared with the general population. Approximately 15 to 38 percent of patients with sporadic LAM have renal AMLs [21-24]. Renal AMLs among patients with LAM also tend to be multiple and bilateral and are more common among patients with TSC-LAM compared with sporadic LAM (88 versus 29 percent in one cohort) [21]. (See "Sporadic lymphangioleiomyomatosis: Clinical presentation and diagnostic evaluation", section on 'Renal angiomyolipomas'.)

PATHOGENESIS AND HISTOPATHOLOGY — AMLs belong to a family of tumors collectively referred to as "neoplasms with perivascular epithelioid differentiation" or "perivascular epithelioid cell tumors" or "PEComas" [25]. AMLs are primarily composed of smooth muscle cells, adipocytes, and epithelioid cells.

Tuberous sclerosis complex (TSC) genes function as tumor suppressor genes, and like in patients with TSC, many sporadic AMLs contain TSC mutations. (See "Tuberous sclerosis complex: Genetics and pathogenesis", section on 'Mechanism of tumor formation'.)

Pathogenesis — The three cell types (smooth muscle cells, adipocytes, and epithelioid cells) appear to be derived from pericytes, which are mural cells that line the microcirculation (capillaries and venules) of the body. Their origin from pericytes is suggested by the fact that they all express pericyte markers (angiotensin II type 1 receptor, platelet-derived growth factor receptor-beta, desmin, alpha-smooth muscle actin, and vascular endothelial growth factor-receptor 2) but not the endothelial cell marker CD31 or the adipocyte marker S-100 [26].

The vasculature within an AML is composed of neoplastic (smooth muscle cells and epithelioid cells) and nonneoplastic (endothelial cells) components. The endothelial cells lining the blood vessels do not appear to originate from pericytes and rather appear to develop independently [27].

Infrequently, AMLs may exhibit characteristics such as local infiltration, extension into the renal vein and/or inferior vena cava, multicentricity, regional lymph node involvement, and rapid local recurrence (if excised). However, the vast majority of lesions have benign characteristics and remain contained.

Additional pathogenetic mechanisms in females — Several clinical observations suggest that female sex hormones promote the growth of renal AMLs. These observations include the increased reported frequency and size of renal AMLs among females, and the increased risk of hemorrhagic complications and growth of AMLs during pregnancy [28-32] or after treatment with exogenous hormone therapy [33].

Histopathology — On histopathology, AMLs are composed of mature-appearing fat, thick-walled and poorly organized blood vessel-like structures, and smooth muscle-like structures in varying proportions [34]. The smooth muscle cells may be seen as appearing to originate from the blood vessel wall in the form of a pinwheel. The blood vessels are thick-walled, similar to arteries, but lack the systematic architectural organization of normal vascular structures.

Variations in histology are common. There are two major histologic variants of AMLs: classic and epithelioid (picture 1) [7,35,36]. In addition, there is a rare cystic variant, called angiomyolipoma with epithelial cysts (AMLEC), which is characterized by solid and cystic areas. Variants are distinguished from each other only by biopsy.

Classic variant – Most AMLs are classic variants [37]. The major features of the classic variant include abnormally thick-walled vessels that lack a well-developed internal elastic lamina and varying amounts of spindle smooth-muscle cells and adipose tissue (picture 1). Any one of the three cell types (ie, smooth muscle cells, adipocytes, and epithelioid cells) may predominate or be virtually absent. In general, epithelioid cells are sparse and make up fewer than 10 percent of cells in the classic variant [37].

Classic AMLs are benign but can be locally invasive, extending into the perirenal fat or, rarely, the collecting system, renal vein, or inferior vena cava and right atrium. Involvement of lymph nodes and/or the spleen is thought to represent multicentricity of origin rather than metastases, since such patients, in general, have no further disease progression on long-term follow-up [38,39].

Epithelioid variant – The epithelioid variant always has an epithelioid cell component (picture 1) [40]. Epithelioid cells are characterized by an abundant eosinophilic and granular cytoplasm. There is no consensus on the percentage of epithelioid cells that is required to make a diagnosis of the epithelioid variant, with values ranging from 10 to 100 percent in published studies [37,41]. Thus, epithelioid AMLs can be composed entirely of epithelioid cells (and lack blood vessels and fat, also called "fat-invisible AMLs") [42]. Alternatively, they can contain variable amounts of adipose and muscle tissue with a significant epithelioid component (generally called "fat poor").

An epithelial component is probably more common in patients who have TSC compared with patients who have sporadic AML. In one case series of approximately 200 patients, epithelioid variants were noted among 25 percent of patients with TSC compared with 6 percent among patients without TSC [37]. TFE3 amplification is occasionally present in epithelioid tumors and may contribute to tumor pathogenesis [43,44].

Unlike the classic variant, the epithelioid variant may be malignant. Although this is infrequent, the risk is greater in patients who have TSC [37,41,45]. Histologic features that suggest an increased risk for malignant transformation include ≥70 percent epithelioid cells, tumor size >7 cm, vascular invasion, ≥2 mitotic figures per 10 high-power fields, atypical mitotic figures, and necrosis [41,46].

Angiomyolipoma with epithelial cysts (AMLEC) – This is a rare cystic variant of AML characterized by solid and cystic areas. AMLEC is a benign lesion with no metastases or recurrence following surgical excision [47].

This variant is characterized by immunohistochemical positivity of the subepithelial stroma for melanocytic markers (HMB45 and melan-A) [47]. These markers help to differentiate this lesion from other cystic renal neoplasms such as multilocular cystic renal cell carcinoma, cystic nephroma, and mixed epithelial and stromal tumor of the kidney.

CLINICAL MANIFESTATIONS — The vast majority of renal AMLs cause no symptoms [7,9]. AMLs usually come to medical attention as an incidental finding on imaging performed for a different indication, or in the case of some tuberous sclerosis complex (TSC) patients, upon serial imaging performed for surveillance [5-7,15,36,48].

The clinical presentation of renal AMLs can differ depending upon whether AMLs are sporadic or associated with TSC [34]. Patients who have sporadic AMLs present in the fourth, fifth, or sixth decade of life, whereas patients with TSC-associated AMLs present earlier, in the third and fourth decades, as a result of surveillance among such patients. Sporadic AMLs are generally solitary, small, and slow-growing. Conversely, TSC-associated AMLs can be large, multiple, bilateral, and have a tendency to grow. In the Tuberous Sclerosis registry to increase disease Awareness (TOSCA) study, among the patients who had TSC-associated renal AMLs, 88 percent had AMLs that were multiple in number and 84 percent had AMLs that were bilateral [8]. One-third of the patients had AMLs that were >3 cm in size. At a mean follow-up of 1.3 years, growth of the AMLs was observed among 21 percent of patients.

Among patients who are symptomatic, features related to hemorrhage appear to be most common. These include abdominal or flank pain (associated with mass effect of the hemorrhage) and tenderness, hematuria, hypertension, anemia, and kidney function impairment [7,11,20,49,50]. Hemorrhage is the most feared clinical complication of AMLs due to its severe nature, often resulting in significant pain, anemia, and sometimes, hemorrhagic shock [51]. Renal AMLs are the most common cause of Wunderlich syndrome, a life-threatening, nontraumatic kidney hemorrhage into the subcapsular and perirenal spaces [52].

The risk of significant hemorrhage is related to the size of the AMLs, degree of vascularity, the size of aneurysms within the AML, and their growth pattern (exophytic growth is associated with a higher risk than endophytic growth) [53]. AMLs that are larger than 6 cm have a higher likelihood of hemorrhage [54]. Increased vascularity and/or an intralesional aneurysm that is 5 mm or larger are also associated with an increased risk of hemorrhage [53,55,56].

In addition, the risk of bleeding is increased among pregnant females, possibly due to a risk of rapid growth induced by hormonal changes and/or increased circulating blood volume and cardiac output associated with pregnancy [28-31]. (See 'Additional pathogenetic mechanisms in females' above.)

Patients with extensive AMLs in association with TSC may develop chronic kidney disease (CKD) and end-stage kidney disease (ESKD) (see "Renal manifestations of tuberous sclerosis complex"). The most common cause of ESKD in such patients is nephrectomy or embolization required to treat symptomatic AMLs [57]. CKD or ESKD in patients with sporadic AML is infrequent.

Epithelioid AMLs can undergo malignant transformation, distant metastasis, and can be associated with local recurrence after removal.

DIAGNOSIS — The diagnosis of renal AML is usually made by imaging. A biopsy of the lesions is usually not necessary, unless the diagnosis is not clear upon imaging or if malignancy is suspected.

Patients who have tuberous sclerosis complex (TSC), sporadic lymphangioleiomyomatosis (LAM), or a combination may have renal AMLs as part of their initial presentation. Thus, all patients will need to undergo further testing to identify underlying TSC. Some will also need to be tested for LAM or TSC-LAM.

When to suspect AML — Most AMLs do not produce symptoms and are diagnosed incidentally on abdominal imaging performed for an unrelated reason. However, AMLs should be suspected among patients who have symptoms and signs of retroperitoneal hemorrhage (eg, flank pain, hematuria, anemia) associated with a mass-like lesion in the kidney. In addition, patients with a history of TSC, LAM, or TSC-LAM who develop such symptoms and signs should be evaluated for a renal AML. (See 'Clinical manifestations' above.)

How to establish a diagnosis — The diagnosis of sporadic AML is usually made by imaging (magnetic resonance imaging [MRI] or CT). In most cases, ultrasound can suggest the diagnosis but is not sufficient to establish the diagnosis. If the diagnosis cannot be made with certainty by CT or MRI, then a needle-guided biopsy of the kidney lesion is appropriate.

Imaging — We preferably use MRI to establish the diagnosis of renal AML. Although not necessary to diagnose AML, administration of gadolinium contrast is used to determine the vascularity of the lesion and detect intratumoral aneurysms. When an MRI is not available or is inappropriate (eg, if the patient has contraindications to MRI or is unable to remain still for the duration of an MRI), then we perform unenhanced and contrast-enhanced CT. We perform an MRI (or CT) even among patients who had the diagnosis of AML suggested by ultrasound. (See "Patient evaluation for metallic or electrical implants, devices, or foreign bodies before magnetic resonance imaging".)

When obtained, MRI and CT should be preferentially performed using a kidney mass protocol (imaging before and at multiple times after the administration of intravenous contrast). The diagnosis of AML depends upon detection of fat within the lesion (image 1) [58-62]. Both MRI and CT are able to identify AMLs that are rich in fat. However, in the subset of AMLs (approximately 5 percent of sporadic lesions) that have a small amount of intralesional fat (ie, "fat-poor" AMLs) [63], MRI may be more sensitive than CT [42,64]. In lesions that lack fat (ie, "fat-invisible" AMLs), no imaging modality can reliably distinguish an AML from an atypical-appearing renal cell carcinoma (RCC) or other malignancy. In such cases, we perform a biopsy for a definitive diagnosis. (See 'Biopsy if imaging is equivocal' below.)

By MRI, fat appears hyperintense (bright) on T1 and T2 sequences without fat saturation and hypointense (dark) on T1 and T2 sequences with fat saturation (image 2 and image 3) [42]. Multiparametric MRI (the use of a variety of sequences including diffusion weighting and chemical shift imaging, among others) can be helpful to more reliably distinguish fat-poor AMLs from other lesions. In a 2020 meta-analysis including over 2000 patients who had an MRI and histopathologic diagnosis of fat-poor AML, MRI had a sensitivity of 83 percent (95% CI 72-90 percent) and specificity of 90 percent (95% CI 84-94 percent) [65].

Unenhanced CT can identify macroscopic fat in AMLs (image 4). Low attenuation values of less than -15 Hounsfield units (HU) in the region of interest are generally indicative of fat [42]. Thinner slices (3 to 5 mm) may be required to detect fat within smaller AMLs. "Fat-poor" AMLs demonstrate high intrinsic attenuation and, after contrast administration, homogenous enhancement, and delayed washout (image 5). The addition of contrast does not improve sensitivity of the diagnosis of AML markedly but may be useful to distinguish AML from other kidney lesions. In a meta-analysis of over 2200 patients who underwent a CT and histopathologic diagnosis of fat-poor AML, CT had a sensitivity of 0.67 (95% CI 0.48-0.81) and a specificity of 0.97 (95% CI 0.89-0.99). The sensitivity estimates of unenhanced and contrast-enhanced CT were comparable (0.81 versus 0.78). However, the heterogeneity between the included studies was high, thereby reducing the confidence in these estimates.

By ultrasound, fat is generally hyperechoic (or hyperreflective) with variable acoustic shadowing [42,66]. However, the appearance on ultrasound of approximately 10 to 30 percent of RCCs is similar to that of AMLs (image 6) [67,68]. In addition, fat-poor AMLs do not have this characteristic hyperechoic appearance and, therefore, can be missed by ultrasound. Thus, using ultrasound for initial diagnosis of AML is usually suboptimal; patients require the diagnosis to be confirmed by MRI or CT. However, among patients already diagnosed with an AML by CT or MRI, ultrasound can be used for monitoring the size of the AML over time.

The main diagnostic challenges by imaging arise for patients who have fat-poor AMLs (classic AML composed predominantly of smooth muscle) and fat-invisible AMLs (epithelioid AMLs). The absence of or limited amount of fat in such lesions limits the ability to diagnose them by imaging alone [64,69]. Alternatively, the fat present within a lesion may be obscured by hemorrhage. The lack of classic appearance may lead to inability to fully distinguish them from RCCs (especially RCCs that invade renal sinus fat giving the appearance of fat in the peripheral part of the lesion) and oncocytomas. In such patients, who generally present with solid kidney masses that do not have an appearance of a classic AML or other lesions, we pursue a biopsy for diagnosis. (See 'Biopsy if imaging is equivocal' below.)

Biopsy if imaging is equivocal — If the diagnosis cannot be made with certainty by MRI or CT, we obtain an image-guided percutaneous core needle biopsy [70]. However, if the lesion is highly suspicious for malignancy because of intratumoral necrosis, intratumoral calcifications, presence of lymphadenopathy, or metastasis, clinicians may elect to surgically remove the lesion rather than perform a diagnostic biopsy [71]. Additional details regarding the biopsy and histopathologic findings are discussed at length elsewhere. (See "Renal manifestations of tuberous sclerosis complex", section on 'Biopsy'.)

Surgical exploration is an alternative among patients in whom percutaneous needle biopsy is not feasible or unsuccessful in securing a diagnosis [70]. The risk of bleeding following needle biopsy of a minimal-fat AML does not appear to be higher than that of a biopsy for other kidney tumors.

The differentiation of renal AML from RCC has become more reliable with the aid of immunocytochemical analysis. Melanocytic markers such as HMB-45 and melan-A are expressed in classic and epithelioid renal AMLs but not in typical RCCs, while epithelial cell-associated markers such as cytokeratin and epithelial membrane antigen are present in RCCs but not in renal AMLs [35,72-74]. A rare variant of RCC with a translocation t(6;11)(p21;q12) expresses HMB-45 and melan-A and is often negative or only focally positive for cytokeratin [75-77].

Additional testing — Some patients with AML may need additional evaluation for TSC or LAM.

Evaluate for tuberous sclerosis complex in all patients — We evaluate all patients with newly diagnosed AML for possible TSC.

The extent of the evaluation depends on the index of suspicion for TSC:

Asymptomatic adult patients who have one or two small (ie, <4 cm) AMLs are less likely to have TSC. Among such patients, it is sufficient to complete a clinical evaluation by obtaining a family history and performing a review of systems and a physical examination. The clinical diagnostic criteria of TSC are presented elsewhere. (See "Tuberous sclerosis complex: Evaluation and diagnosis", section on 'Diagnosis'.)

Patients with multiple (three or more), bilateral, or larger (ie, ≥4 cm) AMLs are more likely to have TSC (image 3). Among such patients, we perform a complete evaluation for TSC (which includes both a clinical evaluation and genetic testing). The diagnostic criteria for TSC are based upon specific clinical features that are discussed elsewhere. (See "Tuberous sclerosis complex: Evaluation and diagnosis", section on 'Diagnosis'.)

Among patients who undergo biopsy, histologic features may also help to distinguish sporadic from TSC-related AMLs. In a single-institution study of 194 renal AMLs in 185 patients, three histologic markers were observed more frequently in patients with TSC: epithelioid-variant AMLs, epithelial kidney cysts, and microscopic AML foci [37]. However, the utility of such markers in identifying patients with TSC has not been proven.

Evaluate for lymphangioleiomyomatosis in some patients — We do not evaluate all patients who present with a sporadic AML for pulmonary LAM. Only a small percentage of patients presenting with a sporadic AML have LAM (image 7). Instead, we would evaluate such patients for LAM only if suggestive findings (ie, pulmonary symptoms, abnormal chest radiograph) were present. (See "Sporadic lymphangioleiomyomatosis: Epidemiology and pathogenesis".)

Conversely, all patients who have LAM should be evaluated for renal AMLs. Approximately 45 to 60 percent of patients with sporadic pulmonary LAM have renal AMLs that tend to be multiple and bilateral [21-24]. The clinical manifestations, diagnosis, and treatment of renal AMLs associated with sporadic pulmonary LAM are similar to those described for renal AMLs associated with TSC. (See "Renal manifestations of tuberous sclerosis complex", section on 'Angiomyolipomas'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cancer of the kidney and ureters" and "Society guideline links: Tuberous sclerosis".)

SUMMARY AND RECOMMENDATIONS

Overview – Angiomyolipomas (AMLs) are uncommon neoplasms occurring in the kidney that are composed of varying amounts of tissues resembling blood vessels, smooth muscle, and adipose. The vast majority of AMLs are benign but malignant transformation of AMLs has been reported. Most AMLs are sporadic. The remainder are mostly associated with tuberous sclerosis complex (TSC); sporadic lymphangioleiomyomatosis (LAM) or a combination of LAM and TSC (TSC-LAM) likely account for a small minority of cases. (See 'Introduction' above and 'Epidemiology' above.)

Pathogenesis and histology – AMLs are primarily composed of smooth muscle cells, adipocytes, and epithelioid cells. These three cell types appear to be derived from pericytes, which are mural cells that line the microcirculation (capillaries and venules) of the body. The vasculature within an AML is composed of neoplastic (smooth muscle cells and epithelioid cells) and nonneoplastic (endothelial cells) components. The endothelial cells lining the blood vessels do not appear to originate from pericytes and rather appear to develop independently. Several clinical observations suggest that female sex hormones promote the growth of renal AMLs. (See 'Pathogenesis and histopathology' above.)

There are two major histologic variants of AMLs: classic and epithelioid (picture 1). In addition, there is a rare cystic variant, called angiomyolipoma with epithelial cysts (AMLEC), which is characterized by solid and cystic areas. Variants are distinguished from each other only by biopsy.

Classic variant – Most AMLs are classic variants. In general, epithelioid cells are sparse and make up fewer than 10 percent of cells in the classic variant. Classic AMLs are benign but can be locally invasive, extending into the perirenal fat or, rarely, the collecting system, renal vein, or inferior vena cava and right atrium.

Epithelioid variant – The epithelioid variant always has an epithelioid cell component. There is no consensus on the percentage of epithelioid cells that is required to make a diagnosis of the epithelioid variant, with values ranging from 10 to 100 percent. Thus, epithelioid AMLs can be composed entirely of epithelioid cells (and lack blood vessels and fat, also called "fat-invisible AMLs"). Alternatively, they can contain variable amounts of adipose and muscle tissue with a significant epithelioid component (generally called "fat poor"). Unlike the classic variant, the epithelioid variant may undergo malignant transformation

Clinical manifestations – The vast majority of renal AMLs cause no symptoms. AMLs usually come to medical attention as an incidental finding on imaging performed for a different indication, or in the case of some TSC patients, upon serial imaging performed for surveillance. Among patients who are symptomatic, features related to hemorrhage appear to be most common. These include abdominal or flank pain and tenderness, hematuria, hypertension, anemia, and kidney function impairment. Hemorrhage is the most feared clinical complication of AMLs due to its severe nature, often resulting in significant pain, anemia, and sometimes, hemorrhagic shock. (See 'Clinical manifestations' above.)

Diagnosis – The diagnosis of sporadic AML is usually made by imaging, preferably MRI with gadolinium contrast. CT without and with contrast enhancement is reasonable when an MRI is not available or is inappropriate. Although ultrasound can suggest the diagnosis, it is not sufficient to establish the diagnosis. (See 'Diagnosis' above.)

The main diagnostic challenges by imaging arise for patients who have fat-poor or fat-invisible AMLs. The absence of or limited amount of fat in such lesions limits the ability to diagnose them by imaging alone. In addition, the fat present within a lesion may be obscured by hemorrhage. The lack of classic appearance may lead to the inability to fully distinguish such AMLs from renal cell carcinomas (RCCs). If the diagnosis cannot be made with certainty by MRI or CT, then we obtain an image-guided core needle biopsy of the kidney lesion. Surgical exploration is an alternative among patients in whom percutaneous needle biopsy is not feasible or unsuccessful in securing a diagnosis, or if the patient has features suspicious for malignancy (eg, intratumoral necrosis, intratumoral calcifications, presence of lymphadenopathy, or metastasis).

Postdiagnostic evaluation – We evaluate all patients with newly diagnosed AML for possible TSC. The extent of the evaluation depends on the index of suspicion for TSC. By contrast, we do not evaluate all patients who present with a sporadic AML for LAM. Instead, we would evaluate such patients for LAM only if suggestive findings were present (ie, pulmonary symptoms, abnormal chest radiograph). (See 'Additional testing' above.)

The postdiagnostic evaluation also includes an assessment of future bleeding risk; this largely informs the decision between treating and surveillance. This is discussed elsewhere. (See "Renal angiomyolipomas (AMLs): Management".)

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Topic 131412 Version 8.0

References

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