Epithelioid angiomyolipoma in a horseshoe kidney: a pediatric tuberous sclerosis case report

Abstract Background Epithelioid angiomyolipoma (EAML) is a rare, potentially malignant PEComa-family tumor strongly associated with tuberous sclerosis complex (TSC). Its fat-poor composition and diffusion restriction on MRI render it indistinguishable from renal cell carcinoma (RCC) without tissue sampling. Case presentation A 7-year-old boy with TSC (TSC2 mutation c.2220 + 1 G > T) was found on routine surveillance MRI to have a new left moiety horseshoe kidney mass with interval growth and restricted diffusion on follow-up imaging four months later. Atypical features for classic AML prompted percutaneous image-guided biopsy. Histopathology confirmed EAML; immunohistochemistry showed HMB-45+, SMA+, S-100−, CD10−, and EMA−, with no histologic features of malignancy. The patient was managed with active surveillance; mTOR inhibitor therapy (everolimus) is planned if further growth occurs. Conclusions In a child with TSC, a fat-poor renal mass with interval growth and diffusion restriction should prompt biopsy rather than assumption of classic AML. The ADC map is a critical imaging discriminator, and the characteristic IHC profile is diagnostic. To our knowledge, this is the youngest published case of biopsy-proven EAML in a horseshoe kidney.