Cytologically malignant margin without continuous pulmonary tumor lesion: cases of wedge resection, segmentectomy and lobectomy

The surgical margin is usually investigated during the operation using a pathological method, though cytological methods are also used to identify remaining malignant cells. We reviewed cases of pulmonary resection for a malignant tumor. At our institution, an on-site surgical margin examination using a cytological method is mandated for cases of wedge resection and segmentectomy, and an option in lobectomy cases. We examined 21 wedge resection (3 primary lung cancer, 18 metastasis), 17 segmentectomy (13 primary lung cancer, 4 metastasis), and 4 lobectomy (all primarily lung cancer) cases. Six cases showed malignant cells in the surgical margin, of which one had a microscopic skip lesion pattern and five an 'occult' pattern (positive cytology, negative pathology). Cytological malignancy occurred even in cases of wedge resection of a tiny (4 mm in diameter) lesion metastasized from colon cancer, as well as segmentectomy with a sufficient gross margin containing microscopic skip lesions and right middle lobectomy with an additional right upper lobectomy due to two previous cytological malignancies in a residual lobe. Surgical margin cytology revealed remaining malignancy in the residual lobe, which provided important information for deciding additional procedures during surgery.