Giant Supratentorial Dermoid Cyst: Radiologic and Histopathologic Diagnosis and Management

Dermoid cysts are rare, benign, congenital lesions that arise from ectodermal remnants [1]. They are typically located in midline intracranial regions such as the posterior fossa or sellar area, but can cause significant clinical symptoms, including mass effect, rupture, or seizures when present in atypical locations [1]. Giant supratentorial non-midline dermoid lesions have been rarely reported in the literature. Here we present a 43-year-old male with a 2-week history of headaches, left-sided weakness, and new-onset seizures. The patient experienced three episodes of seizures and was admitted to the hospital, complaining of headache and numbness. He had no significant past medical history or surgical history. He does not take medications, has no known allergies, and reports occasional alcohol use and smoking two packs of cigarettes per day. On examination, vital signs were stable. Neurological examination showed intact extraocular muscles, clear speech, mild left pronator drift, slow fine motor coordination in the upper extremities, and mildly reduced strength of 4/5 on the left and 5/5 on the right in both upper and lower extremities. He had no difficulty standing on one leg and exchanging legs bilaterally; his tandem gait was intact, and he was able to arise out of a squat independently. The patient's basic metabolic panel and complete blood count were within normal limits, besides a low CO2 level of 19. Initial head computed tomography (CT) revealed a 9.0 cm, hypodense, heterogeneous mass within the parietal lobe with scattered foci of fat density, causing mass effect on the right lateral ventricle and leftward midline shift (Figure 1). The mass contained foci of fat density, measuring approximately 10 Hounsfield units (Figure 1). Subsequent magnetic resonance imaging (MRI) demonstrated a T2 hyperintense, cystic lesion with a lobulated peripheral surface and areas of hyperintensity on T1 (Figure 2). The lesion was non-enhancing post-contrast (Figure 2). Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) demonstrated focal areas of diffusion restriction (Figure 2), and gradient recall echo (GRE) sequences did not demonstrate significant hemorrhagic components. Fluid-attenuated inversion recovery (FLAIR) sequences showed a heterogeneous, “dirty” signal, characteristic of an epidermoid cyst; however, areas that did not restrict diffusion were atypical for an epidermoid cyst (Figure 2). Fine needle aspiration biopsy revealed a moderately cellular cyst lined by squamous epithelium, with pilosebaceous units and keratinaceous debris, consistent with a dermoid cyst (Figure 3) [1]. This distinguishes it from an epidermoid cyst, which lacks dermal components such as sebaceous glands and hair follicles [1]. The patient was started on Decadron and anticonvulsants, showing symptomatic improvement. On Day 5, a right parietal craniotomy was performed, successfully removing the dermoid cyst. Postoperatively, the patient showed significant improvement and was discharged on Day 7 without complications. Dermoid cysts typically present as well-defined, fat-like density lesions on CT and hyperintense on T1-weighted MRI due to their fat content [2]. They are histologically distinct from epidermoid cysts by the presence of dermal components [1]. A potential complication of a dermoid cyst is chemical meningitis if it ruptures, which can be identified by fat-like droplets in the subarachnoid space, ventricles, or sulci [1, 3]. This case emphasizes the role of imaging, histopathology, and surgery in the successful diagnosis and management of dermoid cysts. Written informed consent was obtained from the patient to publish this report in accordance with the journal's patient consent policy. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.