Under the basal-celled type we may clinically have nodular lesions, usually beneath the skin, ulcers, fungi, or warts. The vast majority of the so-called rodent ulcers are basal-celled carcinomata, but occasionally a prickle-celled tumor may run a similar course, differing only in the fact that gland metastases result. Microscopically, the difference is easy to detect, as has already been sufficiently pointed out. Usually the clinical difficulty in diagnosis occurs only in the very early eases. The basal-celled growth has a greater tendency to appear as a subepidermal nodule, its growth is slow, and gradually a scab is formed; the latter comes away and an ulcer appears, or a fungous growth may develop.

Fig. 78.-Prickle-celled carcinoma of the lower lip in a young man, whieh arose after treating a clinically benign lesion with caustic pastes. (Gilchrist's collection).