Keratinous cyst of the palpebral conjunctiva.

A whitish-opalescent, mildly elevated superior tarsal conjunctival lesion measuring 3.0 mm in diameter caused a refractory corneal abrasion in a 54-year-old man. Complete local excision without entering the tarsus produced relief of symptoms. There has been no recurrence during 9 months of follow-up. Histopathologically, a unique keratinous cyst was delimited mostly by basaloid cells resembling the matrical cells in pilomatrixoma. There were no keratohyalin granules in the lining cells, which focally transformed in ghost cells. These histopathologic features are characteristic of trichilemmal keratinization, a heretofore undescribed metaplasia of the conjunctival epithelium.