Tract metastasis in patients with long-term pleural catheter—computed tomography diagnosis and longitudinal assessment

Objectives Long-term indwelling pleural catheters (IPC), used for the management of malignant pleural mesothelioma (MPM), may lead to catheter tract metastasis (CTM). While computed tomography (CT) is valuable for diagnosis, no studies have assessed CT manifestations of CTM. Our goal is to describe the incidence, CT appearances, and temporal evolution of CTM in MPM. Methods A retrospective review of CT of 90 consecutive patients with MPM and IPC. In patients with CTM, a longitudinal assessment was performed for CT appearance at diagnosis and over time, interval from insertion to diagnosis and rate of progression. Results The incidence of CTM was 26% (23/90), in 22 men (54-83 years, mean 73 years). CTM manifested with focal lesion (3 to 60 mm, mean 25 mm) in the subcutaneous tissue at the insertion site. Abnormalities of sub-adjacent skin and fat stranding were present in 16/24 (66%) and 11/24 (46%), respectively, enlargement of chest wall musculature in 11/24 (46%), and dilated subcutaneous vessels in 4/24 (17%) patients. On follow-up, 53% had enlargement of focal lesion. The average rate of progression was 3.5 mm/month, compared to 0.79 mm/month for pleural thickening ( p = 0.03). The time between IPC insertion and CTM diagnosis varied from 58 to 1375 days (median 408 days); 83% occurred after IPC removal. Reporting radiologists described focal abnormality at the insertion site in only 9/23 (39%) patients. Conclusions CTM is commonly overlooked and underreported by radiologists. CT invariably demonstrates focal subcutaneous lesion in the procedure tract, most commonly after IPC removal. Ancillary findings, notably serratus or latissimus dorsi muscle enlargement, are novel finding that can assist in CT detection and diagnosis. Key Points • Catheter tract metastasis (CTM), resulting from indwelling pleural catheter to manage malignant pleural mesothelioma, invariably manifested on CT as a focal subcutaneous lesion at the site of insertion, more commonly after catheter removal. • Ipsilateral muscle enlargement is a newly described CT finding that can assist in the detection and diagnosis. • Catheter tract metastasis was commonly overlooked by radiologists, reported in only 39% of cases.