New York -- In patients with actinic keratoses (AK) of the scalp, treating the surrounding skin will often evoke subclinical lesions that will respond to treatment, according to Deborah F. MacFarlane, M.D., M.P.H.
Dr. MacFarlane, associate professor of dermatology and plastic surgery, M.D., Anderson Cancer Center, Houston, discussed the emerging concept of field cancerization and therapy in an update on non-melanoma tumors of the scalp at an American Academy of Dermatology (AAD) meeting last year.
In addition, she discussed several other topics of increasing interest in primary scalp tumors, including photodynamic therapy and lymphoscintigraphy for determining lymphatic drainage patterns in the head and neck.
She also described the contributions of Mohs micrographic surgery.
"For scalp tumors, this is still the gold standard," she says.
In patients with significant amounts of photodamage and clinically evident AKs, the surrounding skin contains expanded clones of transformed dysplastic cells and subclinical AKs. This is referred to as field cancerization. Such subclinical lesions may regress, remain stable or progress to AKs.
"We find that treatment with topical medications such as imiquimod (Aldara, 3M Pharmaceuticals) will often cause these subclinical lesions to become inflamed, clinically apparent and respond to treatment," Dr. MacFarlane says. "This is field therapy."
Dr. MacFarlane is now using combination treatments in such patients to help prevent progression from AK to in situ squamous cell carcinoma (SCC) to SCC. The combinations include a destructive treatment, such as cryotherapy, followed by a field therapy, such as imiquimod.
"Having patients use self-applied field therapy allows them to participate in their own cancer prevention treatment," Dr. MacFarlane explains.
Dr. MacFarlane predicts interest in photodynamic therapy will grow.
Photodynamic therapy with topically applied ALA is especially good for multiple nonhyperkeratotic AKs, Bowen's disease and superficial basal cell carcinomas (BCCs).
"Essentially, this is the action of a photosensitizing drug by visible light to produce reactive oxygen species within target cells, resulting in their destruction," Dr. MacFarlane says.
Preliminary work indicates that topical ALA accumulates in sebaceous glands and hair follicles, suggesting it may also be useful in the treatment of hair removal, she adds.
On the "cutting edge" for invasive scalp tumors is lymphoscintigraphy. A radioactive tracer is injected intradermally around the cancer site, and a gamma camera takes images until the sentinel nodes are visualized. Intraoperatively, methylene blue dye is injected into the margin of the lesion, and a neoprobe is used to identify radioactive nodes, which often take up the methylene blue.
Suspect lymph nodes are then removed and sent for cytology.
"As lymphatic drainage in the head and neck is often unpredictable, this technique is useful," Dr. MacFarlane says.
RELATED ARTICLE: Primary scalp tumors: clinical tips.
Dermatologic cancer specialist Deborah F. MacFarlane, M.D., M.P.H., provides clinical tips for successful identification of primary scalp tumors. Here, Dermatology Times provides a brief overview of her recommendations:
* When examining the scalp, remove all hairpieces, hair ornaments, etc.
* Be alert to a variety of clinical presentations, such as the psoriatic or seborrheic plaque that does not respond to conventional treatment, or the area of erythema which recurs around a lesion treated with cryotherapy or electrodessication and curettage.
* Check the postauricular area, especially in men.
* Remember that black patients can develop scalp tumors, too.
* Remember that non-melanoma skin cancers have been reported in nevus sebaceous of Jadassohn. More recently, a case of melanoma has been reported with this entity (Abe S et al Br J Plast Surg. 2003 Mar;56(2):171-173).
* Be aware that immunocompromised patients are especially susceptible to having AKs progress quickly to invasive cancers.
* Examine the scalp especially closely in women with thinning hair. "In fact, the appearance of skin cancers in patients with thinning hair questions the theory that skin cancers reflect sun damage from exposure in the first 20 years of life," Dr. MacFarlane says.
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