Angiomyolipoma With Epithelial Cysts.

Angiomyolipoma with epithelial cysts is a rare mesenchymal tumor of the kidney that enters in the differential diagnosis of adult cystic renal neoplasms. These tumors demonstrate a slight female predominance and can present either incidentally or with symptoms, commonly flank pain and hematuria. Unlike conventional angiomyolipoma, this variant is characterized grossly by both solid and cystic areas, and histologically by the presence of single or multiple cysts lined by epithelial cells, a subepithelial "cambium-like" layer of small stromal cells with a prominent capillary vasculature, and a thick exterior wall composed of poorly formed fascicles of smooth muscle and thick-walled dysplastic blood vessels. Tumors show a distinct immunohistochemical profile and are often reactive for melanocytic markers (HMB-45 and Melan-A), as well as estrogen receptor and progesterone receptor. These tumors have an indolent clinical course, with no reports of progression or metastasis in reported cases thus far.