Medium-power microscopy demonstrated a poorly circumscribed tumor consisting of large keratin-filled cysts in the middle and upper dermis and collections of basaloid cells throughout the entire dermis. Some of the tumor cells were organized into ductal structures, while others infiltrated the deepest portions of the dermis as single cells. Dense, hyalinized, desmoplastic stroma separated nests of tumor cells. Tumor extended to the lateral and deep margins of the biopsy specimen. Higher magnification revealed perineural infiltration (Figure 3). Only minimal cytologic atypia was present, and no mitotic figures were identified.
Asymptomatic Cutaneous Lip Plaque—Diagnosis. Arch Dermatol. 2007;143(6):791-796. doi:10.1001/archderm.143.6.791-e