Pleomorphic Hyalinizing Angiectatic Tumor of Renal Hilum

Pleomorphic hyalinizing angiectatic tumor (PHAT) is a recently described rare entity. The tumor histogenesis is proposed to be of primitive undifferentiated mesenchyme. The tumor has a predilection for the subcutaneous soft tissue especially of lower extremity, although other locations have been well documented. We report a case of PHAT arising in the hilum of the kidney, clinically mimicking an infiltrating malignant neoplasm of renal pelvis. The tumor was discovered during workup for unrelated gastrointestinal tract symptoms. Because of the location of the lesion, excision of mass and radical nephrectomy were performed. The tumor had strong immunohistochemical expression of vimentin, CD34, CD99, and vascular endothelial growth factor (VEGF). No additional lesions were documented during 3 years of follow-up. This is consistent with the current thinking that PHAT is a benign neoplasm with increased incidence of recurrence. We document the unique retroperitoneal location of this rare tumor and suggest that PHAT should be considered among the list of unusual lesions at this site.