Introduction Despite the advent of PET scanning and endoscopic minimally invasive methods of sampling mediastinal lymph nodes, surgical assessment, particularly by mediastinoscopy, remains an important tool for staging non-small cell lung cancer.

Methods We carried out a retrospective review of mediastinoscopic lymph node biopsies taken at The Royal Infirmary of Edinburgh between 1996 and 2006 and performed additional histological investigations on select cases.

Results In total, 89/802 (11%) patients had a negative mediastinoscopy but final resection stage of N2/N3. Within this group, 41/89 (46%) patients had positive resection lymph nodes in stations potentially accessible to biopsy at mediastinoscopy. Of these, 30 (34%) patients had had the metastatic station sampled at mediastinoscopy. Further histopathological examination (multiple levels and pancytokeratin immunohistochemistry) of these original biopsies detected micrometastases in two cases, one of which, in retrospect, had been missed on the original section at the time of reporting. Isolated tumour cells were detected by immunohistochemistry in another two cases.

Conclusions Routine examination of additional levels and immunohistochemical staining of mediastinal lymph nodes biopsies is not required and would not improve the overall negative predictive value of the procedure.