Basal cell-signet-ring squamous cell carcinoma of the eyelid.

A 93-year-old woman developed a mass on her right lower eyelid that was present for more than 6 months but underwent rapid expansion during several weeks prior to her ophthalmological evaluation. Examination revealed an approximately 1.8 cm in diameter, fleshy, fungating growth involving more than 60% of the right lower eyelid. Excisional biopsy disclosed a neoplasm arising from the epidermis composed of adjoining basal cell and signet-ring squamous cell carcinoma, without a transition zone. The cells comprising the basal and squamous cell carcinomas were distinct immunophenotypically, with only the basal cell carcinoma reacting with Ber-EP4 and CAM 5.2 antibodies. To our knowledge, this case represents the first example of a collision tumor composed of basal cell and signet-ring squamous cell carcinoma.