Another nodular squamous cell cancer
The central keratin is clearly seen on this otherwise featureless firm red nodule on an elderly white scalp. Keratin must be distinguished from scab; any lesion with broken skin, benign or malignant, can form a slough (or scab) from dried blood and exudate, but only keratin forming lesions grow a hard cutaneous keratin horn like this. This lesion could not be a basal cell cancer (or indeed a melanoma) as they never form well organised keratin horn like this. Some harmless lesions like hypertrophic actinic keratoses, squamous papillomas and a few others can form cutaneous horn but there is too much flesh here to countenance that. Urgent specialist referral to the local skin cancer team is necessary.
Incidentally, SCCs are more common and more aggressive in people on long term immune suppression as in renal transplantation. Its important to know that.