High frequency ultrasound and skin elasticity can
identify skin cancer
2 December 2009
High-frequency ultrasound with elastography can help
differentiate between cancerous and benign skin conditions, according to
a study presented at the annual meeting of the Radiological Society of
North America (RSNA).
Elastography was found to distinguish between benign and malignant
lesions by measuring their
elasticity or stiffness. Since malignancies are stiffer than benign
growths, elastography, when added to high-frequency ultrasound imaging
of the skin, has potential to improve the accuracy of traditional
clinical diagnosis of skin cancers and, in some cases, eliminate
unnecessary biopsies of benign skin lesions. The procedure is
noninvasive, convenient and inexpensive.
"High-frequency ultrasound with elastography has the potential to
improve the efficiency of skin cancer diagnosis," said lead author Eliot
L. Siegel, M.D., vice chairman of the Department of Radiology at the
University of Maryland School of Medicine (UMSM) in Baltimore. "It
successfully delineated the extent of lesions and was able to provide
measurable differentiation among a variety of benign and malignant
There are more than one million cases of skin cancer diagnosed in the
US every year, according to the American Cancer Society. Melanoma, the
most serious type of skin cancer, will account for about 68,720 cases of
skin cancer and 11,590 deaths in 2009, despite the fact that with early
detection it is highly curable.
Suspicious skin lesions are typically diagnosed by dermatologists and
biopsied based on their surface appearance and characteristics.
Unfortunately, even to experienced dermatologists, benign and malignant
lesions often appear similar visually and on physical examination, and
some malignant lesions may have a benign appearance, especially in their
early stages. It is not uncommon for patients to have one or more
lesions that appear concerning.
"Dermatologists tend to biopsy any lesions that seem visually
suspicious for disease," said coauthor Bahar Dasgeb, M.D., from the
Department of Dermatology at Wayne State University in Detroit and
Pinkus Dermatopathology Lab in Monroe, Michigan. "Consequently, many
benign lesions are needlessly biopsied in order to avoid the risk of
missing a potentially deadly melanoma."
An elastogram (left) and ultrasound image (right)
showing squamous cell carcinoma of the skin.
For the study, researchers used an ultra high-frequency ultrasound
system to image 40 patients with a variety of malignant and nonmalignant,
or benign, skin lesions. Malignant tumours included squamous cell
carcinoma, basal cell carcinoma and melanoma. Benign lesions included
dermatofibroma, a noncancerous growth containing scar tissue, and lipoma,
a noncancerous tumour composed of fatty tissue.
The researchers calculated the ratio of elasticity between normal
skin and the adjacent skin lesion, and used laboratory analysis to
confirm their diagnoses. Cystic lesions, which are not malignant,
demonstrated high levels of elasticity, while malignant lesions were
significantly less elastic. The elasticity ratio of normal skin to the
various skin lesions ranged from 0.04 to 0.3 for cystic skin lesions to
above 10.0 for malignant lesions.
In addition, high-frequency ultrasound with elastography allows for
accurate characterization of the extent and depth of the lesion below
the surface, which can aid physicians in treatment.
"The visualized portion of a skin lesion can be just the tip of the
iceberg, and most dermatologists operate 'blindly' beyond what they can
see on the surface," Dr. Siegel said. "High-frequency ultrasound
provides almost microscopic resolution and enables us to get size, shape
and extent of the lesion prior to biopsy."