Acanthosis is term pathologists use to describe an increased number of specialized squamous cells on the surface of a tissue. Acanthosis is commonly seen in the top layer of the skin called the epidermis. Acanthosis can also be seen in the epithelium that lines the inside of the mouth and throat. The increased number of squamous cells causes the epidermis or epithelium to look thicker than normal when examined under the microscope. By itself, acanthosis is a non-cancerous change although it can also be seen in areas near a tumour.