Safety distance in the resection of colorectal lung metastases: AÂ prospective evaluation of satellite tumor cells with immunohistochemistry

ObjectiveAfter complete pulmonary metastasectomy of colorectal lung metastases, tumor recurrence at the site of former resection develops in some patients. Well-described risk factors for local recurrence in the lung include incomplete resection and aerogenous spread of floating cancer cell clusters. The aim of this study was to describe the distribution and frequency of satellite cancer cells or clusters in resected tissue to deduce recommendations for safety margins in the future.MethodsSeventeen colorectal metastases from 10 patients were processed. Evaluation for pattern of growth, satellite cancer cells, and inflammatory reaction at the surface of the metastases was performed on 102 sections with CDX2 and cytokeratin 20 stains. The distance between the surface of the nodule and the satellite cancer cell was measured for each satellite and statistically evaluated.ResultsAs a pattern of growth, interstitial spread, inflammatory reaction, and lymphangitic spread were observed in 41.2%, 35.3%, and 23.5%, respectively. A total of 205 satellite cancer cells were identified in 16 of 17 metastases with a mean distance to the nodule of 0.99 ± 0.85 mm (range, 0.06-6.43 mm). The percentages of satellite tumor cells that are likely to be found within 1.59 mm, 3.43 mm, and 7.4 mm around the nodule are 68.27%, 95.5%, and 99.73%, respectively.ConclusionsSatellite tumor cells, a potential source for local recurrence, are found in a high number around colorectal lung metastases. As a standard of care, a safety distance of 3 mm for small metastases and 8 to 10 mm for larger metastases must be maintained around the lesion to prevent local recurrence.