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 can often appear similar. This results in many benign lesions being needlessly biopsied to avoid the risk of missing a potentially deadly melanoma. In addition, some malignant lesions may have a benign appearance, especially in their early stages.
"High-frequency ultrasound with elastography has the potential to improve the efficiency of skin cancer diagnosis," explained lead author Eliot Siegel, vice chairman of the Department of Radiology at the University of Maryland School of Medicine (Baltimore, MD). "It successfully delineated the extent of lesions and was able to provide measurable differentiation among a variety of benign and malignant lesions."
The study included 40 patients with malignant neoplasms or benign skin lesions. Malignant tumours included squamous cell carcinoma, basal cell carcinoma and melanoma. Benign lesions included dermatofibroma, a non-cancerous growth containing scar tissue, and lipoma, a non-cancerous tumour composed of fatty tissue, and others.
Patients were imaged using an ultrahigh-frequency ultrasound system (14–16 MHz). The researchers calculated the ratio of elasticity between each skin lesion and adjacent normal skin, 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, from 0.4 to 5.0 for benign proliferative lesions, and was above 10.0 for malignant lesions. The technique also enables accurate characterization of the extent and depth of the lesion below the surface.
"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," Siegel said. "High-frequency ultrasound provides almost microscopic resolution and enables us to get size, shape and extent of the lesion prior to biopsy."