CHICAGO — An ultrasound technique that measures tissue elasticity could dramatically alter the way in which skin cancer is diagnosed.
In a prospective study of 56 patients with proliferative malignant neoplasms or benign skin lesions, the use of ultrasound elastography analysis prior to biopsy correctly differentiated benign from malignant lesions in 100% of cases, Dr. Eliot Siegel reported Decthe annual meeting of the Radiological Society of North America.
“We believe that ultrasound has tremendous potential that is completely untapped now to characterize and delineate the extent of skin lesions currently evaluated visually,” he said. “We believe it has tremendous promise to reduce unnecessary biopsies.”
Elastography noninvasively estimates the axial tissue strain, or elastic properties of tissue. Cystic lesions demonstrate high levels of elasticity, while malignant lesions are relatively “hard” with a very low level of elasticity.
Ultrasound with elastography, more so than optical or light images, is unique in its ability to provide the proper depth at which to analyze lesions—around 5 mm below the surface, said Dr. Siegel, vice chair of radiology and a professor at the University of Maryland in Baltimore. This may be useful in the early detection of melanoma before the classic signs such as asymmetry or changes in border are present on the skin's surface. In addition, elastography could have a role during surgery.
“This also could guide the surgeon as the surgeon is doing an excision or biopsy to not just look at the tip of the iceberg that they can see at the skin surface, but actually to be able to look deeper, so they can see exactly which areas they can cut out safely and still remove the entire tumor without unnecessarily removing more than that,” he said.
Elastography software is available on most new ultrasound machines, and has been used with promising results for breast, thyroid, and liver cancer. It has not been used to explore skin lesions, except for one prior study from 2007.
That study used absolute strain values, whereas Dr. Siegel and associates also calculated strain ratios. Malignant lesions had higher strain ratios (minimum 5.3; maximum 32.2), compared to benign lesions (min. 0.01; max. 3). None of the malignant lesions violated a strain-ratio cutoff of 3–5, Dr. Siegel said. He presented a few examples, including a squamous cell carcinoma with a ratio of 13.27 and a benign keloid with a ratio of 1.25.
Although preliminary, the data suggest that strain ratios may also be useful in distinguishing between malignant lesions. Squamous cell carcinomas had a higher ratio overall, said coauthor Dr. Bahar Dasgeb, a radiologist and second-year dermatology resident at Wayne State University in Detroit. Moreover, the strain ratio was higher, even within squamous cell or basal cell cancers, when more invasive cells were present.
If strain ratios are combined with higher ultrasound frequencies, it's possible that the anatomic information gleaned from elastography “could rival the information that a pathologist would see after the lesion was excised,” Dr. Siegel said.
“That's really the direction that we'd like to head into for research and development, as we look at much higher ultrasound frequencies.”
The current study used a clinically available 14–16-mHz ultrasound unit.
Dr. Siegel disclosed receiving research grants from several imaging companies. Dr. Dasgeb had no disclosures.
Elastography estimates the elastic properties of tissue. Malignancies, such as this sqamous cell carcinoma (shown left on elastrogram and right on unenhanced ultrasound) can be differentiated because they are stiffer than benign growths.
Source Courtesy Radiological Society of North America