Smooth Muscle and Adenoma-Like Renal Tumor (SMART)- A Rare Biphasic Renal Tumor with a Review

Smooth muscle and adenoma-like renal tumor (SMART) is a biphasic tumor composed of cytologically bland stromal and epithelial components. It has many histopathological mimickers. A 57-year-old man presented with a left renal mass. The left radical nephrectomy showed a 13.5 cm tumor involving the entire kidney. The microscopic examination showed an unencapsulated, well-circumscribed biphasic tumor composed predominantly of intersecting bundles of smooth muscle, admixed with focal epithelial components arranged in cystic, tubular, tubulopapillary, nests, and cords. Both the components lacked nuclear atypia. Using immunohistochemistry, the spindle cells were positive for SMA and desmin, focally positive for CD10, and negative for ER, PR, and HMB45. The epithelial cells were positive for PAX8 and keratin 7 and negative for CD10. We report an additional example of SMART with a literature review. Knowledge about this recently described entity would lead to a better understanding of the clinicopathological features and histogenesis of this tumor.