Renal epidermoid cyst mimicking renal tuberculous abscess: a case report

Abstract

Renal epidermoid cysts (RECs) are exceedingly rare benign cystic lesions, with only 15 histologically confirmed cases reported worldwide to date. Due to their non-specific clinical and radiological features, they are often misdiagnosed preoperatively as infectious or neoplastic conditions. Here, we report a 25-year-old man in whom a complex renal cyst was incidentally identified during a routine health examination. Retrospectively, the patient reported mild urinary frequency and low-grade fever. Imaging suggested a non-enhancing heterogeneous cyst in the lower pole of the right kidney. Laparoscopic partial nephrectomy was performed, revealing abundant yellow-white caseating material intraoperatively, prompting empirical anti-tuberculosis therapy in the context of regional endemicity. However, histopathological analysis confirmed a diagnosis of RECs, and anti-tuberculous treatment was subsequently withdrawn. On postoperative day 5, the patient developed gross hematuria due to a renal artery pseudoaneurysm, which was successfully managed with selective arterial embolization. This case highlights the diagnostic challenges posed by atypical cystic renal lesions and underscores the importance of integrating imaging, intraoperative findings, and histopathology. Including RECs in the differential diagnosis may prevent unnecessary antituberculous therapy and overtreatment.

Keywords: case report; cystic renal lesion; empirical anti-tuberculosis therapy; partial nephrectomy; pseudoaneurysm; renal epidermoid cyst; renal tuberculous abscess.

Figure 1

Preoperative CT scan: (A) Non-contrast coronal CT image revealed a well-defined mass measuring 7 cm in the right kidney with slightly higher density around the margin. (B) Arterial phase image of contrast-enhanced CT showed no notable enhancement within the lesion. (C) Excretory phase image of contrast-enhanced suggested no contrast agent retention in the cyst and no discernible connection to the pelvis or calyces.

Figure 2

Macroscopic and microscopic pictures of the specimen: (A) Gross appearance disclosed a well-circumscribed solid mass with friable whitish to yellowish amorphous contents. (B) Microscopy revealed the cyst was lined by stratified squamous epithelium (indicated by black arrow) and was filled by lamellated keratin (upper left corner; H&E; ×40).

Figure 3

Postoperative contrast-enhanced CT disclosed an enhancement lesion in the right kidney, suspicious for a RAP (indicated by the black arrow).

Figure 4

Postoperative angiograms. (A) Renal arterial angiogram revealed the formation of RAP. (B) No extravasation of radiographic contrast was found after selective angioembolization.