Each of the tissues in the penis contains several types of cells. Different types of penile cancer can develop in each kind of cell. The differences are important because they determine the seriousness of the cancer and the type of treatment needed.
Almost all penile cancers start in skin cells of the penis.
Squamous Cell Carcinoma
About 95% of penile cancers develop from flat skin cells called squamous cells. Squamous cell cancers can develop anywhere on the penis. Most of these cancers are found on the foreskin (in men who have not been circumcised) or on the glans. These tumors tend to grow slowly. If they are found at an early stage, these tumors can usually be cured.
This is an uncommon form of squamous cell cancer that can occur in the skin in many areas. A verrucous carcinoma growing on the penis is also known as Buschke-Lowenstein tumor. This cancer looks like a large benign genital wart. These cancers tend to grow slowly but can sometimes grow very large. They can invade deeply into surrounding tissue, but they rarely spread to other parts of the body.
Carcinoma in situ (CIS)
This is the earliest stage of squamous cell cancer of the penis. In this stage the cancer cells are only found in the top layers of skin. They have not yet grown into the deeper tissues of the penis. Of the glans, it is sometimes called erythroplasia of Queyrat and on the shaft of the penis (or other parts of the genitals), it is called Bowen’s disease.
Melanoma is a type of skin cancer that starts in melanocytes, the cells that make the brownish color to the skin that helps protect it from the sun. These cancers tend to grow and spread quickly and are more dangerous than other types of skin cancer.
Basal cell cancer is another type of skin cancer that can develop on the penis. It makes up less than 2% of penile cancers. This type of cancer is slow-growing and rarely spreads to other parts of the body.
Adenocarcinoma (Paget Disease of the Penis)
This very rare type of penile cancer can develop from sweat glands in the skin of the penis. It can be very hard to tell apart from carcinoma in situ of the penis. At first, the cancer cells spread within the skin. Later, cells can invade, growing into the tissues underneath the skin and spreading to lymph nodes.