Use of strain ratio in evaluating superficial soft tissue tumors on ultrasonic elastography

The aim of this study was to describe the strain ratio in histopathologically confirmed superficial soft tissue tumors using ultrasonic elastography (USE).

From March to August 2012, 94 soft tissue tumors in 79 consecutive patients (age range 19-70 years) were examined using USE for palpable masses. Among them, 39 lesions in 36 patients were histopathologically confirmed. Thirty-four lesions in 31 patients with lipoma, ganglion, epidermal inclusion cyst, and pilomatricoma were included: 34 histopathologically confirmed mature lipomas (n = 19), ganglia (n = 6), epidermal inclusion cysts (n = 5), and pilomatricomas (n = 4). Ultrasonographic features of margins, echogenicity, walls, ultrasonic transmission, and vascular flow via Doppler ultrasonography were evaluated. The strain ratios were calculated from the USE strain measured within the lesion and in adjacent tissue. Intraclass correlation (ICC) with Cohen's kappa was used to determine intraobserver agreement, and the strain ratios of the three groups were compared using Mann-Whitney U tests. All statistical analyses were performed using R package statistical software, and p values <0.05 were considered to be statistically significant.

On USE, repeated measurements of the strain ratios showed excellent intraobserver agreement [ICC value = 0.952 (CI 0.905-0.977), p < 0.05]. The strain ratios of lipomas (median ± standard error 0.83 ± 0.18) were statistically different (p < 0.05) from those of ganglia, epidermal inclusion cysts, and pilomatricomas. The strain ratios of ganglia (2.78 ± 0.48) were also statistically different (p < 0.05) from those of epidermal inclusion cysts and pilomatricomas. The strain ratios of epidermal inclusion cysts (0.17 ± 0.21) were not statistically different (p > 0.05) from that of pilomatricomas (0.13 ± 0.02).

Strain ratios determined by USE help to differentiate lipomas and ganglia from other superficial soft tissue tumors. Our results suggest that USE could be used in addition to traditional ultrasound techniques to obtain diagnostic clues in the evaluation of superficial soft tissue tumors.