Epidermoid Cyst Located in Facies Convexa Cerebri with Atypical Images

To the Editor: Epidermoid cyst, was first described by an artist in a French medical school in 1807, [1] is a kind of congenital disease characterized by a stratified epithelial capsule and laminated keratin debris contents. It accounts for approximately 1% of all intracranial tumors and commonly locates in the cerebellopontine angle, parasellar region, and the fourth ventricle. Cerebrospinal fluid density on magnetic resonance imaging (MRI) with nonenhancing is their typical images. However, epidermoid cysts occurring in an uncommon location with atypical MRI may cause the difficult diagnosis. While the radiological and pathological features of atypical epidermoid cysts have still been unclear, we reported an epidermoid cyst that was located in facies convexa cerebri and presented with atypical images. A 17‑year‑old girl was experienced for few minutes' unconsciousness, three times in recent 3 months. Each time before faint, she could feel intermittent numbness in both lower limbs, developing from distal to proximal, following some moderate to intense exercise. No positive family history was obtained. Physical examination revealed that the only neurological positive sign was hypoesthesia in her left lower extremity. Lesion showed block mass in parietal lobe closed to the parietal bone with iso‑ or hypo‑intensity on T1‑weighted MRI, and hyperintensity on T2‑weighted MRI. There was no empty shadow in the lesion due to the absence of vascular flow and the boundary remained clear. Middle structure shifting was not found. Simultaneously, remarkable enhancing was not discovered after Gd‑diethylenetriamine pentaacetic acid administration [Figure 1a‑1c]. Lesion also showed the hyperintense signal on diffusion‑weighted imaging (DWI). Meanwhile, magnetic resonance spectroscopy (MRS) showed low creatine, choline, N‑acetylaspartate (creatine and N‑acetylaspartate were obvious), and inverted peak of lactate. The patient underwent surgery by right parietal approach to the parietal lobe. Tumor with pearly appearance, approximately 3 cm × 3 cm × 3 cm, was in facies convexa cerebri. Taking attention to protecting superior sagittal sinus and avoiding rupture of the cyst, the neurosurgeon totally resected the tumor. Yellow and cheese‑like cyst contents emerged after splitting the tumor. Intraoperative frozen pathology declared keratosis and squamous epithelium with the consideration of epidermoid cyst. Slight numbness in the left leg was left over without any other neurological deficits after operation. During the hospitalization, unconsciousness was not relieved. The patient was discharged on the 7 th day after surgery without any neurological deterioration. On the day of discharge, postoperative pathology also confirmed diagnosis of epidermoid cyst according to remarkable …