| Abstract: | In recent years, fine-needle-aspiration biopsies (FNA) have been widely used in the evaluation of renal masses, with false-positive FNA data being very uncommon. We present a case report of a 76-yr-old man with a 16-cm renal cyst and what was interpreted as an isolated calcified mural nodule. Following drainage of the main cyst fluid, FNA biopsy showed atypical cell clusters thought to be positive for malignancy. Subsequent surgery failed to disclose either a residual mural nodule or evidence of malignancy. Immunoperoxidase studies performed on both the cell block and actual cyst wall suggested that the abnormal cells were histiocytes. The diagnostic pitfalls of this case, along with a review of pertinent literature, are discussed. Diagn Cytopathol 1994; 11:380–384. © 1994 Wiley-Liss, Inc. |
