PMC6376515_01
MRI of a nasal dermoid cyst with intracranial extension in a cat. The cyst and contents were heterogeneously hyperintense on T2- and T1-weighted (T2W and T1W, respectively) imaging (white arrows) with rim contrast enhancement following administration of gadolinium. The lesion extended through the cribriform plate (red arrow). (a) Sagittal T2W; (b) transverse T2W; (c) dorsal T1W pre-contrast; (d) dorsal T1W post-contrast (gadolinium)
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Brain MRI revealed a well-demarcated, bi-lobed mass measuring 19.5 mm in length extending from the caudal nasal cavity through the cribriform plate and into the calvarium contacting the left olfactory bulb and frontal lobe (Figure 1).
Sagittal CT image of the skull of a cat with a nasal dermoid cyst showing a midline fusion defect of the nasal cavity allowing communication with the subcutaneous space (large arrow) and extension of the defect through the cribriform plate (small arrow)
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Photomicrograph of fine-needle aspirate cytology of the contents of a nasal dermoid cyst in a cat showing a hair fragment (black arrow) and degenerate neutrophils, macrophages, lymphocytes and blood (white arrow) stained with Wright's Giemsa
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Cytology of fine-needle aspirates (FNAs) of the mass (CT-guided through the defect) revealed rafts of pigmented and non-pigmented squames, degenerate neutrophils, vacuolated macrophages, lymphocytes, plasma cells and multinucleate giant cells in a proteinaceous background containing small amounts of blood (Figure 3).
Photomicrograph of histology of the intracranial portion of a nasal dermoid cyst with intracranial extension removed surgically. The cyst was characterised by well-differentiated stratified squamous keratinising epithelium with a granular cell layer (arrow), keratin accumulation (star) and apocrine gland structures (not pictured here)
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Histopathological analysis confirmed the nasal and intracranial masses were cystic structures filled with abundant keratin and lined with squamous epithelium and embedded apocrine glands and hair follicles, along with a few neutrophils and cocci bacteria, consistent with a diagnosis of an infected dermoid sinus/cyst (Figure 4).