A rare mimicker of a complex cystic lesion of the liver – hepatic epidermoid cyst with biopsy correlation

Hepatic epidermoid cysts are very rarely encountered congenital benign lesions. These cysts have a fibrous wall that is lined by stratified squamous epithelium with no adnexal structures. They often show overlap with other hepatic cystic lesions, hence are challenging to diagnose preoperatively. It is important to be aware of this entity firstly due to its diagnostic ambiguity and secondly due to its rare potential of showing malignant transformation. We present a case of a 54-year-old male who presented with non-specific upper GI complaints. All laboratory values, such as liver function tests, were within normal limits. Ultrasound examination revealed an incidentally detected well-defined isoechoic lesion in the right lobe with a hypoechogenic rim, mimicking a solid lesion; however, there was no evidence of internal vascularity. A triple-phase computed tomography was performed to further characterize the lesion, which demonstrated a subtle peripheral enhancement in venous and delayed phases. No calcification or daughter cysts were seen. No evidence of any perilesional hyperemia was observed. Magnetic resonance imaging showed a T1 hypointense, T2 hyperintense cystic lesion showing diffusion restriction, suggesting keratinaceous content, raising a high suspicion for an epidermoid cyst, although other complex cystic lesions still remained as differentials. Due to the diagnostic uncertainty, a biopsy was performed, and histopathology sections showed the cyst wall lined by keratinized stratified squamous epithelium with large intraluminal flakes of laminated keratin. Multimodality imaging can aid in preoperative diagnosis and help avoid unnecessary surgical intervention in selected patients.