Bilateral mixed epithelial stromal tumor in an end-stage renal disease patient: the first case report

Although first intimated in the 1970s, mixed epithelial stromal tumor has been recognized as a diagnostic entity for less than 10 years, with an identity that has been challenged by overlap between other cystic renal neoplasms, most notably with cystic nephroma. We report the first case of a bilateral mixed epithelial stromal tumor occurring in a 41-year-old dialysis-dependent woman, notably also the first case reported in a patient with end-stage renal disease. The neoplasms occurred 5 years apart and were diagnosed as mixed epithelial stromal tumor in both instances. We describe the presentation and pertinent radiologic, histologic, and immunophenotypic findings of these neoplasms with a review of the current debate regarding mixed epithelial stromal tumor and cystic nephroma taxonomy.