Background: Recently, several case reports have described a rare but distinct subtype of renal tumor, referred to as a "low grade renal epithelial neoplasm," that appears to have a better prognosis than conventional renal cell carcinoma does. This report describes the cytologic features of this tumor as determined by fine needle aspiration (FNA) biopsy.
Case: A 53-year-old woman with a history of lymphoma had a renal mass incidentally discovered on an abdominal computed tomographic scan performed for lymphoma restaging. Results of an FNA biopsy showed relatively uniform, medium-sized tumor cells with moderate amounts of finely vacuolated or wispy cytoplasm and indistinct cell borders. The nuclei were primarily round with coarse chromatin and had prominent nucleoli. In the cell block preparation, the tumor cells showed a tubular architecture and an abundant myxoid matrix. The patient underwent a partial nephrectomy. The tumor was classified as a low grade myxoid renal epithelial tumor.
Conclusion: This unusual kidney tumor appears to have distinctive cytomorphologic features, including a uniform population of epithelial cells with round nuclei, an abundant myxoid matrix and tubular architecture.