Correlation of Ki-67 indices from biopsy and resection specimens of neuroendocrine tumours

INTRODUCTION Neuroendocrine tumours (NETs) are a heterogeneous group of tumours with a highly variable presentation and prognosis. Management decisions are complex. Ki-67 levels in tissue samples are a key indicator used to grade tumours and guide treatment. This study assessed whether the Ki-67 index and tumour grade generated from tissue samples correlated with that assessed in resection specimens. METHODS This was a retrospective cohort analysis of all patients who had both a tissue sample and a resection specimen analysed in our trust, a tertiary referral centre, during 2012 and 2013. RESULTS Data from 36 patients were reviewed. Ki-67 indices from tissue samples and resection specimens showed strong correlation (r=0.95, p<0.001). Tumour grading was the same in the tissue sample and resection specimens for 22 patients (61.1%). In four patients (11.1%), the tissue sample overestimated the grade while in ten (27.8%), the sample underestimated the grade. CONCLUSIONS In most cases, the Ki-67 index and tumour grade from the tissue sample matched that of the resection specimen. However, in nearly 40% of cases, the tissue sample grading did not match the resection tumour grading. In the majority of these, the tissue sample underestimated disease activity. A low Ki-67 index in a tissue sample should therefore be taken as provisional and should not, in isolation, persuade clinicians to choose a more conservative treatment approach if there is clinical, biochemical or radiological evidence suggestive of a more aggressive disease pathology.