By Diane Mapes
AC/DC guitarist Angus Young may pretend his index fingers are devil's horns in live concerts, but human beings have actually been known to sprout a horn or two.
Called cutaneous horns (cutaneous is Latin for "of the skin"), these growths occur when the surface of the skin thickens, usually in response to some type of disease.
Sometimes the diseased or damaged layer of skin can blister or become white and scaly, similar in appearance to a psoriasis outbreak. Or it can become as thick as the hide of an elephant or a rhinoceros.
"The topmost part of the skin is the stratum corneum — it protects the body," says Dr. Clay J. Cockerell, clinical professor of dermatology at the University of Texas Southwestern Medical Center in Dallas. "But if the stratum corneum is damaged due to disease or something along those lines, then it can actually make a different kind of layer."
The most famous case of cutaneous horns is possibly the so-called "tree man" of Indonesia. The "tree man" has an extremely rare genetic defect that, after exposure to the human papillomavirus (HPV), causes his skin to produce massive amounts of cutaneous horns. At least 13 pounds of these warts were removed from his body last year.
Often, the diseased skin can grow into the shape of a horn.
"Sometimes, especially if there's a tumor beneath the skin's surface, it can form a very thick cornified layer in an upward spine or spike," says Cockerell.
Cutaneous horns may be disturbing to see, although they're fairly uncommon. A retrospective study by the Royal Liverpool Hospital came up with only 643 cases worldwide between 1970 and 1989.
These skin horns are made of compacted keratin, the same type of material that comprises your fingernails, toenails and hair. Most often found on the parts of your body that are exposed to the sun and where skin cancer develops. About 30 percent of cutaneous horns sprout on the face or scalp, with 60 percent of the growths due to benign lesions. The rest are derived from malignant or premalignant epidermal lesions. Horns are equally prevalent in men and women, and are more common — and more malignant — in people between the ages of 60 and 75.
"Most commonly, we see these develop over a squamous cell carcinoma, but we also see horns overlying warts," says Cockerell.
Since cutaneous horns develop atop various skin lesions — including cancerous skin, burn scars, warts and venereal warts — they can grow anywhere on the body. Cutaneous horns have been found on the head, scalp, nose, eyelid, ear, lip, chest, neck, shoulder, forearm, leg and hand, according to a 2004 study in the world Journal of Surgical Oncology.
There have even been cases of cutaneous horns on the penis, such as that of a 70-year-old Indian man who suffered multiple penile horns, according to a 2003 study in an Indian medical journal.
As with anything on the body, cutaneous horns come in all shapes and sizes. Some can be microscopic, others can become quite large.
"We've seen some that can be the size of a small pickle," says Cockerell. "Others were about the size of a small banana."
For example, in 2005, the journal of the Head and Neck Surgery Foundation reported the case of a 58-year-old Greek man with a giant cutaneous horn in front of his right ear. The horn, which had reportedly been growing for three years, reached the size of a finger before it was surgically removed.
Cutaneous horns caused by a tumor or cancer typically require surgery. Small lesions can be removed with liquid nitrogen or a topical medication.
In the past, horned humans were cause for awe, alarm and the inevitable sideshow attraction.
One of the earliest reports was in in 1588, involving an elderly Welsh woman by the name of Margaret Gryffith. Gryffith appeared on the stage in London as a "Miraculous and Monstrous" woman, out of whose forehead "there groweth a crooked Horne, of four ynches long." According to Jan Bondeson, who documented the case in his book, "The Two-Headed Boy and Other Medical Marvels," her head horn was such a popular draw that Queen Elizabeth's Privy Council took time off from their preparations for the Spanish Armada to go see her.
Then there was a 16th-century Frenchman, Francois Trouvillou, who sported a large curved growth like a ram's horn on his head. After he was expelled from his village for witchcraft, he made it to Paris where he became huge sensation on the stage.
More recently, in 1930, a Chinese farmer with a 14-inch long horn growing out of the back of his bald head was known as the Wang, the Human Unicorn.
If you suspect the odd protuberance growing out of your head or hand or genital area is a cutaneous horn, it's a good idea to see a doctor right away.
"The horn is a red flag … it's almost always a sign of an underlying growth of some kind," says Cockerell. "In many cases, it's cancer."