Ultrasound suitable for soft-tissue mass triage

Dec 23, 2008

Ultrasound can be a useful triage tool for evaluating soft-tissue masses, according to research from Leeds Teaching Hospitals NHS Trust in Leeds, U.K.

"Ultrasound is a cost-effective, accurate, and accessible method for the triage of soft-tissue masses, directing patients to the most appropriate management pathway," said Richard Robinson. He presented the research during a scientific session at the 2008 RSNA meeting in Chicago.

Noting that soft-tissue masses were a common cause of imaging referral from both primary and secondary care clinicians and that the majority of lesions are benign, the institution sought to study the efficacy of ultrasound for first-line investigation of these masses.

The Leeds researchers prospectively studied 358 consecutive patients who had received ultrasound exams requested by family and hospital clinicians over a six-month period. The studies were performed by five experienced musculoskeletal radiologists using a high-frequency linear probe. The radiologists were not blinded to patient clinical history.

For each lesion, the radiologists recorded characteristics such as lesion size, fascial relationship, anatomical location, internal echogenicity, relationship with bone and neurovascular structures, external margins, and presence or absence of internal vascularity, Robinson said.

A provisional ultrasound diagnosis was then made for each mass using one of eight categories. Categories 1 to 5 represented benign lesions, while lesions in category 6 were atypical lipomas requiring further evaluation. Category 7 included indeterminate lesions and category 8 included possible sarcomas, according to Robinson.

Patients with lesions graded in categories 6 to 8 received an MRI exam within 14 days of the ultrasound exam. All category 8 lesions were also referred to the institution's multidisciplinary sarcoma service for urgent clinical evaluation. Patient follow-up was performed using the institution's clinical, radiological, and pathological databases over the following two-year period, Robinson said.

Of the patients, 284 had lesions initially classified as benign (categories 1 to 5) on ultrasound and were sent back to the referring doctor or were given a suggested referral to an appropriate nonsarcoma specialist. Sixteen patients were subsequently re-referred to sarcoma services because of recurrent "concerning" symptoms, Robinson said.

Of these 16 patients, 11 received MR exams three to 12 months from the ultrasound exam; all were diagnosed as having benign lesions. Four patients subsequently underwent surgery, with lipomas confirmed histologically, he said.

Sixty-two of the 74 patients with lesions graded as categories 6 to 8 underwent MRI. Forty-nine of these cases were deemed to be benign, with 10 suspected carcinomas and three indeterminate lesions. Overall, six of 10 lesions deemed possible sarcomas were eventually determined to be malignant.

Correlation between MR and ultrasound was considered exact or moderate in the majority of patients, with poor correlation seen in three patients. Ultrasound suggested an aggressive lesion in those cases, while MRI showed a benign diagnosis, Robinson said.

"US can fill the role as a triage tool between primary care presentation and specialist referral, offering rapid patient reassurance, fast tracking of more suspicious lesions, and increased diagnostic confidence in combination with focused MRI," he concluded.

By Erik L. Ridley
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