Mesenchymal neoplasms of the kidney encompass a wide range of tumor types with heterogeneous clinical, histologic, and molecular features. Given their rarity relative to renal epithelial neoplasms, diagnosis may be challenging. In this review, the clinicopathologic and molecular characteristics of selected mesenchymal neoplasms of the adult kidney are discussed, including benign entities with diverse lines of differentiation (such as juxtaglomerular cell tumor, angiomyolipoma, and anastomosing hemangioma), sarcomas (synovial sarcoma, leiomyosarcoma, Ewing sarcoma), and tumors with variable biologic potential (solitary fibrous tumor). Mesenchymal lesions that may arise in peri-nephric soft tissue (including well differentiated / dedifferentiated liposarcoma and perinephric myxoid pseudotumor of fat) are also highlighted, given their potential to present as a ‘renal’ mass.
William J. Anderson (Wed,) studied this question.