Pigmented Squamous Cell Carcinoma of the Skin: Report of Two Cases and Review of the LiteratureJurado, I. M.D.; Saez, A. M.D.; Luelmo, J. M.D.; Diaz, J. M.D.; Mendez, I. M.D.; Rey, M. M.D.The American Journal of Dermatopathology: December 1998 - Volume 20 - Issue 6 - p 578-581 Extraordinary Case Reports Abstract Author Information Melanoma is the most common malignant tumor in which melanin synthesis occurs, although other nonmelanocytic tumors synthesize melanin or contain nonneoplastic melanocytes. We present two cases of infiltrating pigmented squamous cell carcinoma of the skin and review the clinical, morphologic, and ultrastructural features. Melanin was found in epithelial tumor cells as well as in macrophages and dendritic melanocytes. Interestingly, one of the neoplasms was associated with an adjacent melanocytic nevus and pigmented solar keratosis. Immunohistochemical analysis showed that neoplastic cells stained for keratin and melanin-filled dendritic cells were found to be S-100 protein and HMB45 positive. A careless examination of the immunohistochemical stains for S-100 protein and HMB45 could cause the misdiagnosis of melanoma, a neoplasm that has a more ominous outlook. From the Departments of Pathology (I.J., A.S., J.D., I.M., M.R.) and Dermatology (J.L.), Consorci Hospitalari del Parc Taulí, Sabadell, Barcelona, Spain. Address correspondence and reprint requests to Dr. Ismael Jurado Troyano, Department of Pathology, Consorci Hospitalari del Parc Taulí, Parc Taulí s/n 08208 Sabadell, Barcelona, Spain. © 1998 Lippincott Williams & Wilkins, Inc.