title: Trichilemmal carcinoma of the upper eyelid.
abstract: BACKGROUND
  Trichilemmal carcinoma (TLC) is a rare adnexal tumour related to the external hair sheath. We describe the first case of TLC on the upper eyelid to be treated with Mohs micrographic surgery.
  
  
  METHODS
  A 65-year-old man presented with a 2-month history of a firm 4 mm left upper eyelid nodule. An incisional biopsy revealed an infiltrative, lobulated tumour composed of large, polygonal, clear cells. A diagnosis of trichilemmal carcinoma was made and the patient underwent Mohs micrographic surgery. At follow-up 2 years later, there was no evidence of recurrence.
  
  
  CONCLUSIONS
  The pathogenesis of TLC remains unclear, with actinic damage, longterm low dose irradiation and transformation from benign trichilemmoma having been postulated. Trichilemmal carcinomas must be differentiated from other malignant clear cell tumours of the eyelid and the correct diagnosis made promptly as TLC takes an indolent clinical course, in which metastasis is a rare event, despite the tumour's cytologically malignant appearance. We recommend Mohs micrographic surgery as a treatment modality for this tumour, due to its potential for locally aggressive growth and local recurrence.
mesh_terms: D000368:Aged; D018280:Carcinoma, Skin Appendage / Q000473:pathology* / Q000601:surgery; D005142:Eyelid Neoplasms / Q000473:pathology* / Q000601:surgery; D006197:Hair; D006801:Humans; D008297:Male; D015580:Mohs Surgery; D012878:Skin Neoplasms / Q000473:pathology* / Q000601:surgery