Basal cell carcinoma of the eyelid with exceptional histomorphologic expressions.

A basal cell carcinoma of the eyelid had unique and potentially confusing histopathologic features. The tumor displayed a carcinoma in situ pattern with replacement of an extensive segment of the tarsal epithelium by neoplastic basaloid cells, a finding to the best of the authors' knowledge that has not been previously documented. Within the infiltrating component of the dermis were classical solid basaloid nests and lobules; they were accompanied, however, by a separate and exceptionally prominent component of duct-like (pseudoglandular) units mimicking a microcystic adnexal carcinoma.