Adult Renal Hamartomas

Abstract Introduction

Angiomyolipoma Leiomyoma Conclusions

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Introduction

Hamartomas are neoplasmlike masses of disorganized but mature specialized cells or tissue normally found in a particular organ (1, p 243). There is disagreement regarding whether renal hamartomas actually represent choristomas, which are defined as ectopic rests of normal tissue (2,3,4). The ectopic nature of the lesion may be a question of degree. For example, in an angiomyolipoma one would expect to find smooth muscle, fat, and vessels within the kidney; however, fat would not normally be seen within the cortex, the site of most of these lesions. Although such a distinction matters little in terms of clinical relevance, there is a general consensus that hamartomas are not neoplasms. The term renal hamartoma is commonly used to refer to a variety of renal masses, including mesoblastic nephroma, fibroma, myolipoma, lipoma, leiomyoma, and, most frequently, angiomyolipoma (4,5).

Mesoblastic nephroma, also called fetal renal hamartoma or leiomyomatous hamartoma, does not occur in adults and is not discussed here. Fibromas are small (less than 10 mm in diameter) benign lesions found incidentally in the renal medulla at autopsy (1, p 986) and are rarely clinically apparent. Myolipomas and pure lipomas of the kidney are extremely rare (6) but may lie on a continuum with angiomyolipoma and leiomyoma (4), which are more common. Although nearly always distinct pathologic entities, angiomyolipoma and leiomyoma occasionally share some histologic and morphologic characteristics. The fact that lesions in either group often contain both smooth muscle and fat indicates that they may represent points on a continuum of subtle histologic variation. Both angiomyolipoma and leiomyoma may be present at birth and continue to grow during childhood and early adulthood. These benign lesions frequently manifest as incidental findings but, if sufficiently large, may cause mass effect on adjacent organs and therefore potentially produce symptoms.

In this article, we discuss the clinical, pathologic, and histologic characteristics of renal angiomyolipoma and leiomyoma and present their typical and atypical imaging appearances, along with correlative pathologic material. We also address clinical management issues for these tumors.

Abstract Introduction

Angiomyolipoma Leiomyoma Conclusions

Source Information References