About the penis

The penis contains several types of tissue, including skin, nerves, smooth muscle, and blood vessels. A thin tube called the urethra starts at the bladder and runs through the center of the penis. Urine and semen come out through the urethra. The head of the penis is called the glans. At birth, the glans is covered by a piece of skin called the foreskin, or prepuce. The foreskin is often removed in infant boys in an operation called circumcision.

Inside the penis are 3 chambers that contain a soft, spongy network of blood vessels. Two of these cylinder-shaped chambers, known as the corpora cavernosa, lie on either side of the upper part of the penis. The third lies below them and is known as the corpus spongiosum. This chamber widens at its end to form the glans. The corpus spongiosum surrounds the urethra, a tube that carries urine from the bladder through the penis. The opening at the end of the urethra is called the meatus.

When a man gets an erection, nerves signal to his body to store blood in the vessels inside the corpora cavernosa and corpus spongiosum. As the blood fills the chamber, the spongy tissue expands, causing the penis to elongate and stiffen. After ejaculation, the blood flows back into the body, and it becomes soft again.

Semen is made up of fluid produced by the seminal vesicles and the prostate gland plus sperm cells that are made in the testicles. It is stored in the 2 small sacs near the bladder and prostate known as the seminal vesicles. During ejaculation, semen from the seminal vesicles passes into the urethra and out the meatus at the tip of the penis.

Cancers of the penis

Each of the tissues in the penis contains several types of cells. Different types of penile cancer (cancer of the penis) 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.

Squamous cell carcinoma

Penile cancer starts in the skin of the penis. Almost all (about 95%) 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.

Verrucous carcinoma is an uncommon form of squamous cell cancer that can occur in the skin in many areas. When it is found on the genitals, verrucous carcinoma is also known as Buschke-Lowenstein tumor. This cancer looks a lot like a benign genital wart. These cancers tend to grow slowly. They can spread deeply into surrounding tissue, but they rarely spread to other parts of the body.

The earliest stage of squamous cell cancer of the penis (or any other organ) is called squamous cell carcinoma in situ (CIS). 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. Depending on the exact location of a CIS of the penis, doctors may give additional names to the disease. CIS of the glans is sometimes called erythroplasia of Queyrat. The same condition when found on the shaft of the penis (or skin of other parts of the body) is called Bowen disease.

Adenocarcinoma: Cancers that start in glandular cells are called adenocarcinomas. This rare type of penile cancer can develop from sweat glands in the skin of the penis. Paget disease of the penis is a condition in which adenocarcinoma cells are found in the penile skin. At first, the cancer cells spread within the skin. Later on, these cells can invade, growing into the tissues underneath the skin and then spreading to lymph nodes. Paget disease can also affect skin in other areas, but most often involves skin around the anus, vulva, and the breasts. (This condition should not be confused with Paget disease of the bone, an entirely different disease also named after Dr. James Paget.)

Melanomas

Melanoma is a type of skin cancer that starts in the cells that produce the pigment that gives skin color (melanocytes). These cancers tend to grow and spread rapidly and so are more dangerous than other types of skin cancer. Although melanomas are most often found in sun-exposed skin, they do rarely occur in other areas. Less than 2% of penile cancers are melanomas. For more information about melanoma and its treatment, please see the American Cancer Society document, Melanoma Skin Cancer.

Basal cell penile 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.

Sarcomas

A small number of penile cancers develop from the blood vessels, smooth muscle, and other connective tissue cells of the penis and are called sarcomas. This document does not further discuss sarcoma. For more information about this type of cancer, please see the American Cancer Society document, Soft-Tissue Sarcoma.

Benign and precancerous conditions

Sometimes, growths can develop on the penis that are abnormal but are not cancers (they are benign). Some of these growths are considered pre-cancers because they can turn into true (invasive) cancers over time if they are not treated. These lesions can look like warts or irritated patches of skin. Like penile cancer, they are most often found on the glans or on the foreskin, but they can also occur along the shaft of the penis.

Condylomas

These are wart-like growths that look like tiny cauliflowers. Some are so small that they can only be seen when the skin is viewed under a magnifying lens. Others may be as large as an inch or more in diameter. Condylomas are caused by infection with human papilloma virus (HPV).

Penile intraepithelial neoplasia

In this condition, dysplastic (abnormal) cells are seen only in the surface layer of the penile skin. Erythroplasia of Queyrat and Bowen disease, which are types of carcinoma in situ (CIS), are also forms of penile intraepithelial neoplasia (PIN). Another form of this condition is known as bowenoid papulosis. These types of PIN can exist for years before turning into real squamous cell cancer of the penis.

Last Medical Review: 07/11/2008
Last Revised: 05/13/2009