We describe a novel cystic renal
tumor consisting of benign epithelial and malignant stromal components in a 56-year-old woman who was admitted to hospital with macroscopic
hematuria. Enhanced computed tomography revealed a multilocular 3.4 × 2.7-cm
tumor in the center of the left kidney. After total left
nephrectomy, the excised
tumor appeared extensively cystic with a well defined border on the cut surface. Histologically, the
tumor was composed of biphasic a benign epithelial lining on tubules or
cysts with a typically hobnailed appearance, and anaplastic sarcomatous stroma with frequent mitosis. Periepithelial cuffing of the
sarcoma cells was evident without an epithelial-stromal transition. Carcinomatous nests, blastemic elements, ovarian-like stroma or differentiated mesenchyme were not evident in the stroma. The epithelial cells were reactive with cytokeratins,
epithelial membrane antigen (EMA),
vimentin and
transducin-like enhancer
protein 1 (TLE1). Stromal cells were reactive with
vimentin, CD99 and TLE1, partly reactive with CD34 and CD10, and non-reactive with cytokeratins, EMA,
Wilm's tumor protein (WT-1),
estrogen receptor (ER),
progesterone receptor (PgR), CD57, HMB45 or Bcl2. SYT-SSX fusion gene was not detected with reverse transcription polymerase chain reaction. Because these findings did not coincide with established descriptions of cystic
renal neoplasms, we preferred the term, '
adenosarcoma'. This could become a new classification for adult cystic renal
tumors.