Differentiation between staple line granuloma and recurrence after sublobar resection for primary lung cancer

Background: The use of sublobar resection for early-stage lung cancer or frail cases that cannot tolerate radical surgery for primary lung cancer has been increasing. This study aimed to identify the frequency, shape, and course of staple line thickening and granuloma formation after sublobar resection for primary lung cancer, and to identify factors that help distinguish them from recurrent cancer cases. Methods: The medical records of 64 patients who underwent sublobar resection for primary lung cancer from January 2012 to December 2017 at our institution were retrospectively reviewed. Computed tomography (CT) images taken every 6 months for at least 3 years after surgery were reviewed, and the postoperative course was examined. Results: Staple line thickening at the time of the first CT scan after surgery was observed in 43 cases (67.2%). Of them, linear thickening was seen in 31 cases (72.1%), and nodular thickening was seen in 12 cases (27.9%). Of these 43 cases, 25 cases were decreased, 8 cases were unchanged and 10 cases showed a tendency to progress during the follow-up period. Of the 64 cases, 7 (10.9%) had staple line recurrence. Staple line recurrence was significantly correlated with vascular invasion (P=0.015), surgical margin (P=0.013), nodular thickening (P<0.001) and a tendency to show progressive thickening (P<0.001). Conclusions: Staple line thickening was observed in many cases of sublobar resection, and most of them were linear thickening. Staple line recurrence should be suspected if nodular thickening appears and shows a tendency to progress.