Two biopsy specimens from the upper lip showed similar microscopic features. The epidermis was normal. Variably shaped, irregular islands and nests of basaloid cells with peripheral palisading filled the reticular dermis and approached the deep skeletal muscle at the base of the biopsy specimen. Within the nests, there were attempts at follicle formation, and papillary mesenchymal bodies were present. The surrounding stroma was fibroblastic; there was no separation artefact.
Other findings included superficial vascular ectasia, lobules of sebaceous cells at the base of the tumor (adjacent to muscle), a solitary eccrine duct within the tumor, and a single keratin-filled cystic structure with focal calcification.
Plaques on the Face of a 26-Year-Old Woman With Usher Syndrome. Arch Dermatol. 2001;137(2):219-224. doi: