Lung transthoracic ultrasound elastography imaging and guided biopsies of subpleural cancer: a preliminary report

Background: Despite the usefulness of elastography in assessing the stiffness/elasticity of tissues, and its proven diagnostic accuracy in thyroid, breast, and prostate cancers, among others, it is not yet applied in transthoracic ultrasound (TUS) scans to investigate lung nodules.

Purpose: To investigate the potential clinical utility of TUS elastography in diagnosing lung cancer proven by fine-needle aspiration biopsy (FNAB).

Material and methods: TUS elastography was performed in 95 consecutive patients (71 men, 24 women; age, 62.84 ± 7.37 years) with lesions suspected of involving the chest wall or the pleura detected on chest X-ray or computed tomography (CT). Patients with pleural effusions were not enrolled, but were further evaluated by pleural fluid cytology. Patients were excluded from the study if a diagnosis had already been made based on sputum cytology and/or bronchoscopic histology (making TUS biopsy unnecessary) or if their lung lesions could not be visualized under standard US. Under FNAB, 34 consolidations were ascribed to pneumonia and 65 to cancer. Under TUS, tissue stiffness, detected using a convex multifrequency 2-8-mHz probe and a MyLab™Twice - ElaXto, was scored from 1 (greatest elasticity) to 5 (no elasticity). Subpleural solid masses (2-5 cm) were initially detected by TUS and subsequently assessed by FNAB.

Results: Histological diagnoses were: small cell lung cancer (4/61), adenocarcinoma (29/61), squamous cell carcinoma (SCC) (12/61), large cell lung carcinoma (12/61), and lymphomas (4/61). Patients' age and mass sizes (3.06 ± 0.88 cm) were not significantly associated with any histological type. A significant lower elasticity of SCC (4.67 ± 0.492) was observed versus other types of lung cancer (P < 0.005), and versus pneumonia (2.35 ± 0.48).

Conclusion: Since only squamous cell lung carcinoma displays the feature of significantly reduced elasticity, and since no clear-cut diagnostic key is yet available, the clinical usefulness of TUS elastography is currently limited with a view to characterizing tumors. Nevertheless, it does enable good non-invasive imaging of lung nodules, providing information on their stiffness, and can improve the accuracy and yield of FNAB.