Less Common Types of Skin Cancer and Skin Conditions

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Most skin cancers are one of four types. These most common types amounting to 99 percent of all skin cancers include:

  • Basal Cell Carcinoma
  • Squamous Cell Carcinoma
  • Keratoacanthomas
  • Melanoma

Less common types amounting to less than one percent of all skin cancers include:

  • Merkel cell carcinoma
  • Kaposi sarcoma
  • Skin adnexal tumors
  • Cutaneous lymphoma
  • Sarcomas

Skin Conditions Sometimes Developing Into Skin Cancer

There are also skin conditions that sometimes develop into skin cancer or are actually early stages of skin cancer. These include actinic keratosis and squamous cell carcinoma in situ.

Actinic Keratosis

Actinic keratosis (AK) is a precancerous skin condition from high sun exposure. AKs appear as rough, scaly spots, usually on the face, ears, backs of hands or arms of middle-aged or fair-skinned people. People usually develop multiple spots of actinic keratosis.

These spots grow slowly. They cause no symptoms, aside from some possibly being itchy or sore. Many go away on their own. They can return after seeming to go away.

Some AKs develop squamous cell skin cancer. Most do not, but treatment is the best action to ensure cancerous ones do not progress unnoticed. You need these spots checked regularly for signs of skin cancer.

Squamous Cell Carcinoma in Situ

Also called Bowen disease, squamous cell carcinoma in situ is early squamous cell skin cancer. “In situ” means the cancerous cells only exist in the upper layer of skin and have not invaded other layers. This cancer appears as red patches, many over ½ inch across. They are redder, crustier and scalier than AKs. The only symptoms of Bowen disease may be some itching or soreness. But most Bowen disease causes no symptoms.

Bowen disease usually appears on sun-exposed skin areas. But it also appears in anal and genital area skin, such as in cases of human papilloma viruses (HPVs). Doctors usually treat Bowen disease to prevent possible progression to invasive squamous cell skin cancer.


Benign Skin Tumors

Benign skin tumors are not cancerous. There are many types of benign skin tumors, including most moles, seborrheic keratosis, benign blood vessel growths called hemangiomas, soft tumors of fat cells called lipomas and warts.

Doctors need to screen your skin spots and other abnormalities of your skin, to ensure skin cancer is not present. This is particularly true if you notice skin spots or discoloration that changes size or shape.