Based on the CT appearance and USG appearance (which revealed an echogenic lesion) - the most important differential diagnosis was a small oncocytoma/lipid-poor angiomyolipoma. However, the possibility of RCC can not be ruled out. Since the patient has a history of left-sided breast cancer (now completely treated and patient disease-free for 5 years), although unlikely, however, the possibility of metastasis is also there. CT thorax was performed which did not reveal and metastasis. However, it is clear that this lesion needs excision.

Laparoscopic nephron-sparing resection of the right renal tumor was performed near the hilum, posterior-medial. 

HPE reveals 2.5 X 1.5 X 0.6 cm tumor. The microscopic examination reveals epithelioid and spindle cells in palisades and interlacing fascicles. Thick-walled vessels with hyalinized walls present. Smooth muscles and entrapped adipose tissue present.

Tumor cells are Melanin -A positive, SMA positive, and Cytokeratin negative.

Thus a diagnosis of spindle cell tumor - consistent with angiomyolipoma.