Published online Jan 16, 2023. doi: 10.12998/wjcc.v11.i2.417
Peer-review started: October 7, 2022
First decision: November 4, 2022
Revised: November 16, 2022
Accepted: December 21, 2022
Article in press: December 21, 2022
Published online: January 16, 2023
Processing time: 96 Days and 21.9 Hours
Angiomyolipoma (AML), the most common benign tumor of the kidney, is usually composed of dysmorphic blood vessels, smooth muscle, and mature adipose tissue. To our knowledge, AML with cystic degeneration has rarely been documented. Cystic degeneration, hemorrhage, and a lack of fat bring great challenges to the diagnosis.
A 60-year-old man with hypertension presented with a 5-year history of cystic mass in his left kidney. He fell 2 mo ago. A preoperative computed tomography (CT) scan showed a mixed-density cystic lesion without macroscopic fat density, the size of which had increased compared with before, probably due to hemorrhage caused by a trauma. Radical nephrectomy was performed. Histopathological studies revealed that the lesion mainly consisted of tortuous, ectatic, and thick-walled blood vessels, mature adipose tissue, and smooth muscle-like spindle cells arranged around the abnormal blood vessels. The tumor cells exhibited positivity for human melanoma black-45, Melan-A, smooth muscle actin, calponin, S-100, and neuron-specific enolase, rather than estrogen receptor, progesterone receptor, CD68, and cytokeratin. The Ki-67 labeling index was less than 5%. The final diagnosis was a fat-poor renal AML (RAML) with prominent cystic degeneration.
When confronting a large renal cystic mass, RAML should be included in the differential diagnosis.
Core Tip: Angiomyolipoma (AML) is a clinically common benign kidney tumor. The majority of classic AMLs can be diagnosed preoperatively through radiological technology because of the appearance of an adipose component. We report a rare case of a fat-poor renal AML (RAML) with prominent cystic degeneration. The establishment of RAML diagnosis is challenging because of the lack of specificity of imaging features. Histopathological and immunohistochemical examinations show that the three classic components express AML markers, supporting the final diagnosis.