Pulmonary Staple-Stump Granuloma After Segmentectomy: Two Case Reports and Comparison with Cases of Stump Recurrence

BACKGROUND Correctly diagnosing a staple-line mass after pulmonary resection for lung malignant tumor can be difficult. Differential diagnoses of recurrence, infectious mass, granuloma, and so on must be considered, despite their rarity. We report two cases of pulmonary staple-stump granuloma after segmentectomy for lung cancer. CASE REPORT Case 1 involved a 70-year-old man with small nodule in the left upper lobe identified on computed tomography (CT). Video-assisted thoracoscopic (VATS) left upper division segmentectomy was performed. Histopathological examination revealed squamous carcinoma. Follow-up CT 1 year postoperatively showed a shadow at the staple-stump, with growth evident later. CT-guided biopsy found no malignancy. However, complete left upper lobectomy was performed because of the gradually enlarging lesion. Histopathological examination revealed epithelioid granuloma. Case 2 involved a 60-year-old with suspected lung cancer in the right upper lobe. VATS right upper division segmentectomy (S2) was performed. CT at 30 months postoperatively showed a shadow at the staple line, with subsequent growth. VATS right upper lobectomy was performed. Intraoperative rapid diagnosis revealed epithelioid granuloma. These two cases were compared with five cases of staple-stump recurrence in our institution. All cases of recurrence grew concentrically or radially from the staple line with the mass surrounding the staple line. On the other hand, cases of granuloma extended along the long axis of the staple line, and 3-dimensional CT (3DCT) may help to understand the morphology. CONCLUSIONS Although preoperative differentiation of staple-line granuloma is difficult and pathological diagnosis is important, characteristic radiologic features and 3DCT may facilitate diagnosis.