December 08, 2007

Penile Cancer

The penis contains several types of tissue, including skin, nerves, smooth muscle, and blood vessels. Running through the inside of the penis is a thin tube called the urethra. 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 consists of fluid produced by 2 small sacs near the bladder and prostate (the seminal vesicles) and by the prostate gland. It contains sperm cells that were made in the testicles. This fluid is produced and stored in the seminal vesicles. During ejaculation, semen from the seminal vesicles passes into the urethra and out 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.

Epidermoid carcinoma: Penile cancer develops in the skin of the penis. About 95% of penile cancers develop from flat skin cells called squamous cells. Penile tumors tend to grow slowly. If they are found at an early stage, these tumors can usually be cured. Squamous cell penile cancers can develop anywhere on the penis but most develop on the foreskin (in men who have not been circumcised) or on the glans.

Verrucous carcinoma is an uncommon form of squamous cell cancer that can occur on the male or female genitals, skin, mouth, larynx, and anus. Verrucous carcinoma of the genitals is sometimes also called a Buschke-Lowenstein tumor. It looks a lot like a benign (noncancerous) genital wart (see the section "Benign and Precancerous Conditions" for more information). These low-grade cancers can spread deeply into surrounding tissue, but they rarely spread to other parts of the body.

Adenocarcinoma, a very 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. The cancer cells at first spread within the skin, but they may eventually invade underneath the skin and spread to lymph nodes. Paget disease can affect skin anywhere in the body but most often affects skin of the perianal area (tissues of or 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.)

The earliest stage of squamous cell cancer of the penis (or any other organ) is called squamous cell carcinoma in situ (CIS). Penile CIS is contained entirely within the skin of the penis and has not yet spread to 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.

Melanomas: About 2% of penile cancers develop from pigment-producing skin cells called melanocytes. Cancers of these cells are called melanoma. These cancers are more dangerous because they grow and spread more rapidly. Melanomas usually develop from sun-exposed areas of skin. Although sun exposure is an important risk factor for melanoma, a few of these cancers can develop on the penis or other areas not likely to become sunburned.

Basal cell penile cancer: Basal cell cancers represent less than 2% of penile cancers. They are slow-growing tumors that rarely spread to other parts of the body.

Sarcomas: The remaining 1% of penile cancers are sarcomas, cancers that develop from the blood vessels, smooth muscle, and other connective tissue cells of the penis.

Benign and Precancerous Conditions

Sometimes abnormal benign (not cancerous) growths develop on the penis. Some of these benign growths may eventually evolve into invasive cancer if they are not treated. These precancerous conditions can resemble warts or irritated patches of skin. Like penile cancer, they usually develop on the glans or on the foreskin, but they can also occur along the shaft of the penis.

Condylomas are wart-like growths that resemble tiny cauliflowers. Some are so small that they are apparent only when the skin is viewed under a magnifying lens. Others may be as large as an inch or more in diameter.

Squamous cell cancer of the penis usually forms slowly over many years, and it is usually preceded by precancerous changes that may last for several years. The medical term for this precancerous condition is penile intraepithelial neoplasia, or dysplasia. "Intraepithelial" means that the precancerous cells are confined to the epithelium (surface layer of the penile skin).

Adapted from: American Cancer Society

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