Renal Core Biopsies of Angiomyolipomas: Review of a Single Institution Eight Year Experience with an Emphasis on Angiomyolipomas with Epithelioid Features
Angela J Wu, Stuart Wolf, Scott Tomlins, Rohit Mehra, L Priya Kunju. University of Michigan, Ann Arbor, MI
Background: With the increased use of image guided core biopsies (cbx) of renal masses, cbx of benign entities such as angiomyolipomas (AMLs) are being encountered. AMLs on cbx can present both diagnostic and therapeutic implications when epithelioid features are present; our goal was to review our experience with cbx of AMLs with an emphasis on AMLs with epithelioid features (eAMLs).
Design: The clinical, radiologic, morphologic and immunohistochemical features of all cbx with a diagnosis of AML from 1/2004 to 10/2012 at our institution were reviewed.
Results: Thirty five AMLs were diagnosed on cbx (an incidence of <1% of all biopsied renal masses). The most common indication for cbx was unusual radiographic features, usually lipid poor/solid appearing masses (mean size=2.9 cm; 1.3-6 cm). One patient had tuberous sclerosis. Seven (20%) were diagnosed as eAML; the remainder were diagnosed as classic AML. Only 4 (11%) AMLs, all with a cbx diagnosis of eAML, were excised; of these, 3 and 1 case had an excision diagnosis of eAML and classic AML respectively. The most helpful features on cbx in predicting an excision diagnosis of eAML were: a high percentage of atypical epithelioid cells (at least 70-80%), epithelioid cells arranged in sheets with minimal to absent intervening fat or spindled smooth muscle, and a paucity of large dysplastic appearing vessels; features not present on cbx were marked atypia, necrosis, or increased mitoses. Immunohistochemistry was performed in 40% (14/35) of all cbx, including all cbx with a diagnosis of eAML. None of the AMLs in our study metastasized and of the AMLs which were excised, only one (with an excision diagnosis of eAML) recurred (median followup 20.5 months).
Conclusions: In our experience, ruling out RCC in cbx of eAML was a morphologic dilemma in a subset of cases but was usually easily ruled out with immunohistochemistry. The most common diagnostic dilemma on cbx was distinguishing classic AML from eAML; the most helpful features were the presence of a high proportion of atypical epithelioid cells arranged in sheets with a paucity of intermixed smooth muscle, fat, and dysplastic vessels.
Category: Genitourinary (including renal tumors)
Wednesday, March 6, 2013 9:30 AM
Poster Session V # 139, Wednesday Morning