Figure 934

Tuberous sclerosis complex (TSC): kidney involvement. Contrast-enhanced CT, A, and gadolinium-enhanced T1 weighted magnetic resonance images, B, of a 15-year-old woman with TSC, show both a large, hypodense, heterogeneous tumor in the right kidney (arrows) characteristic of angiomyolipoma (AML) and multiple bilateral kidney cysts. Kidney cysts had been detected at birth.

AML is a benign tumor composed of atypical blood vessels, smooth muscle cells, and fat tissue. While single AML is the most frequent kidney tumor in the general population, multiple and bilateral AMLs are characteristic of TSC. In TSC, AMLs develop at a younger age in females; frequency and size of the tumors increase with age. Diagnosis of AML by imaging techniques (ultrasonography [US], CT, magnetic resonance imagine [MRI]) relies on identification of fat into the tumor, but it is not always possible to distinguish between AML and renal cell carcinoma. The main complication of AML is bleeding with subsequent gross hematuria or potentially life-threatening retroperitoneal hemorrhage.

Cysts seem to be restricted to the TSC2 variety (see Fig. 9-35) [33]. Their extent varies widely from case to case. Occasionally, polycystic kidneys are the presenting manifestation of TSC2 in early childhood: in the absence of renal AML, the imaging appearance is indistinguishable from ADPKD. Polycystic kidney involvement leads to hypertension and renal failure that reaches end stage before age 20 years. Though the frequency of renal cell carcinoma in TSC is small, the incidence is increased as compared with that of the general population. (Courtesy of J. F. De Plaen and B. Van Beers.)

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