Metanephric adenosarcoma: a rare case with immunohistochemistry and molecular analysis.

BACKGROUND

Metanephric neoplasms comprised a spectrum of kidney tumors containing renal epithelial or stromal cells or both, including metanephric adenoma, metanephric stromal tumor, and metanephric adenofibroma. The majority of cases were benign; only one case of "metanephric adenosarcoma" had been reported in the English literature.

HISTORY

We present the case of a 69-year-old man who developed a neoplasm composed of renal epithelial component identical to metanephric adenoma combined with malignant spindle-cell stroma. The epithelial component was positive for CD57, AE1/AE3, but negative for WT-1, CD56, SYN, and CgA; whereas the sarcomatous component was negative for epithelial markers, SMA, Caldesmon, MyoD1, Myogenin, and S-100; and positive for vimentin, CD10, and WT1 focally. No specific sarcoma differentiation was apparent in the stroma by immunohistochemistry, and no SYT-SS18 rearrangement or BRAF mutation was detected by molecular analysis.A diagnosis of metanephric adenosarcoma was made because of the morphological features and immunohitochemistry and molecular pathology analysis.

CLINICAL SIGNIFICANCE

We believe that metanephric adenosarcoma should be in the expanded spectrum of metanephric neoplasia as a malignant stromal variant.

CONCLUSIONS

We report a rare case of metanephric adenosarcoma with immunohistochemistry and molecular analysis and emphasize the histopathologic features and differential diagnosis of the rare lesion to promote a better and broader understanding of this less understood subject.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_179.