The proliferating trichilemmal cyst (PTC)is a tumor that originates from
hair follicles. It is almost always benign, but rare lesions have been reported with
malignant potential. In the present case, the patient had a mass on the right side of her
neck for a few years, which suddenly increased in size. Cytologic examination revealed
many atypical squamous cells staining well with orange G and light green, suggestive of
a squamous cell carcinoma. Total extirpation was performed under general anesthesia,
gross pathology revealing a focally cystic tumor approximately 5 cm in diameter. The
final diagnosis was malignant PTC from the characteristic features. We here report
cytologic findings for this case with regional lymph node metastasis