One of the common skin cancers of horses is squamous cell carcinoma (SCC). SCC is usually a locally aggressive, metastatic cancer requiring early diagnosis and treatment to prevent spread. Other, less serious, conditions that may resemble SCC is habronemiasis, chronic skin infections and proud flesh (excessive granulation tissue). Horses with white skin seem to be particularly susceptible to SCC.

SCC often appears as a tumor or ulcer on the skin. SCC can be differentiated from less serious conditions by its irritated or bleeding appearance. It is commonly found around the eye or in the eye itself, on the prepuce or penis and around the vulva. Positive diagnosis requires biopsy. If the history does not include a wound prior to the development of the tumor, proud flesh or habronemiasis is unlikely, and rapid treatment is recommended.