[Cytology of percutaneous aspiration biopsy of renal angiomyolipoma: a study of 4 cases].

Percutaneous aspiration biopsy of renal angiomyolipoma (AML) was carried out on four patients to investigate the cytological features of AML. The diagnosis was confirmed histologically after the removal of the tumor. The specimen was fixed in 95% alcohol and stained by the Papanicolaou's method. Cells obtained formed clusters in three of four cases. Cells originating from leiomyomatous element of AML varied in their size, but are usually small with small oval nuclei and rich cytoplasm of lacy appearance. The cytoplasm was fragile and the cell border was not clear. Nuclear chromatin was not increased and was distributed diffusely. Fat cells originating from fatty element of the tumor were mature type and obtained from all of three patients who had much typical lipomatous element in the tumor. In conclusion, cytology of aspiration biopsy is useful to establish preoperative diagnosis of AML in such occasions when there are difficulties in differential diagnoses between AML and renal cell carcinoma even by either computed tomography, angiography or ultrasonography.