TSC1 splicing mutation in renal angiomyolipoma with epithelial cysts without fat: A very rare case report and literature review.

Renal angiomyolipoma is a benign mesenchymal tumor that can be divided into classical and other subtypes. Angiomyolipoma with epithelial cysts (AMLEC) is an extremely rare non classical subtype. AMLEC without fat component is even rarer. We report a case of AMLEC without fat in a 29-year-old man who was provisionally diagnosed with cystic renal carcinoma by ultrasonography, abdominal enhanced CT and MRI. He had no complaints, or personal or family history of TSC, or other malignancies. Based on imaging findings, robot-assisted laparoscopic nephron-sparing partial nephrectomy through a retroperitoneal approach was performed for the purpose of both diagnosis and treatment. We diagnosed AMLEC after considering the differential diagnosis of other cystic renal neoplasms, such as cystic renal carcinoma, multilocular cystic renal cell neoplasm of low malignant potential, adult cystic nephroma and mixed epithelium and stromal tumor. Meanwhile, the whole-exon sequencing (WES) results showed insert-splicing mutation in the 21st exon and 20th exon of the TSC1 gene. No treatments were performed after the operation and no evidence of recurrence or metastasis at regular follow-up.