Cancer is Abnormal Cell Growth.
All tumor cells show the six hallmarks of cancer.
- Cell growth and division absent the proper signals (Dys-regulated)
- Continuous growth and division even given contrary signals (Autonomous)
- Avoidance of programmed cell death
- Limitless number of cell divisions
- Promoting blood vessel construction
- Invasion of tissue and formation of metastases
Now this can apply to any cell of body to produce distinct syndromes producing clinical syndromes based on site of abnormal growth and type of cell undergoing neoplastic change. In case of skin as tissue any cell can undergo neoplastic change -
skin lymphoma is a neoplastic transformation of immune cells which are found in all sites of body but also have discrete organs like lymph nodes which are sites of naive cells & sites of immune reactions. therefore skin can also host immune cells which can be
- in-situ transformation (undergo neoplastic change at site) or
- may metastasized from distant lymph node or extranodal site after undergoing neoplastic transformation.
Regarding Differences b/w two or any skin cancer- there are many at every level be it - pathology, clinical s/s, treatment & prognosis. At every level there is difference b/w tumors originating from different cell types- So much so that even Lymphomas of skin are so many types that classification of lymphomas is evolving still.
But most basic difference is that immune cells may not considered be structural component of skin (even though they are) but other skin cancers are directly originating from skin cells per se.
Regarding the incidence of skin cancer types - the cancer ,mentioned in your reference are really the most common types of skin cancers. cf lymphomas. another reference is https://www.aad.org/media/stats-skin-cancer