DIAGNOSTIC DIFFICULTIES IN THE INTERPRETATION OF NEEDLE ASPIRATION MATERIAL FROM LARGE RENAL CYSTS

In recent years, fine-needle-aspiration biopsies (FNA) have been widel y 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 sh owed atypical cell clusters thought to be positive for malignancy. Sub sequent surgery failed to disclose either a residual mural nodule or e vidence 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 revie w of pertinent literature, are discussed. (C) 1994 Wiley-Liss, Inc.