Malignant proliferating trichilemmal tumor of the lower eyelid

Purpose: To report on the first case of malignant proliferating trichilemmal tumor (PTT) on the eyelid, and to describe the clinical and histopathologic findings. Methods: Interventional case report and literature review. Results: A 42-year-old woman presented with a 2-year history of a firm, 3 × 2 cm lower eyelid mass. The mass was excised with the frozen section control. The defect in the lower eyelid was reconstructed with modified Hughes tarsoconjunctival flap and skin graft from the left postauricular area. Histopathologic examination revealed the proliferation of outer hair sheath epithelium with multiple central areas of trichilemmal keratinization. The presence of marked cellular atypia and frequent mitoses indicated the malignant transformation. Conclusions: Malignant PTT has not yet been reported on the eyelid. Malignant PTT should be included in the differential diagnosis for eyelid tumors.