腎臟黑色素血管周圍上皮樣細胞瘤(PEComa)：罕見案例報告及文獻回顧

游家豪¹、溫玉清^1,2

1臺北市立萬芳醫院泌尿科－委託臺北醫學大學辦理

2臺北醫學大學泌尿學科

Melanotic perivascular epithelioid cell tumor (PEComa) arising from kidney : A rare case report and literature review

Chia-Hao, You¹, Yu-Ching Wen^1,2

1 Department of Urology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan

2 Department of Urology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan

Introduction:

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor defined by the World Health Organization as “mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells” which sharing the characteristics of smooth muscle and melanocytic markers. PEComa can display an aggressive clinical course and the origin of the kidney is rare with only few cases being reported. The image features of pigmented renal PEComa is nonspecific, usually mimicking renal cell carcinoma, and the biologic behavior is undetermined.

Presentation of case:

We reported a case of 30-year-old female patient without any underlying disease. She reported intermittent right flank pain for 7-8 months. During the annual health examination, incidental finding of right renal mass lesion with size about 5.6cm in length was noted from abdominal CT. The following MRI of kidney revealed right kidney tumor with intra-tumor hemorrhage and no obvious fat component was noted. Due to renal cell carcinoma unable to be ruled out, she was then admitted for the operation with right laparoscopic radical nephrectomy and the pathology result disclosed TFE-3 rearranged PEComa.

 Discussion and conclusion:

 According to the present literatures, the the melanotic PEComas shared with nonmelanotic TFE-3 rearranged PEComas their epithelioid morphology, relative lack of smooth muscle differentiation, and their preponderance of HMB45 over Mart-1/Melan-A expression. As for the differential diagnosis, other heavily pigmented neoplasms should be considered, including malignant melanoma, cellular blue nevi, and pigmented epithelioid melanocytomas. However, the melanocytic neoplasms would show strong expression of SOX10 and S100 while uncommon in PEComa. Otherwise, renal cell carcinoma (RCC) with either  TFE-B or TFE-3 fusion should also be considered but the RCC not typically show the extensive melanin accumulation. PEComas may be benign or malignant and the formal criteria were not well-established. The presence of 2 or more features, including size > 5 cm, an infiltrative growth pattern, high nuclear grade and cellularity, mitotic rate of ≥ 1/50 HPF, necrosis, and vascular invasion may present more aggressive clinical course. It is worth noting that TFE3-rearranged RCC is an aggressive tumor subtype with the poorer prognosis than papillary RCC. As more cases are identified, it will be important to determine whether aggressive behavior is a general feature of TFE-3-rearranged PEComas.