Molecular quantification and mapping of lymph-node micrometastases in cervical cancer

Background A proportion of patients with cancer and lymph nodes negative on histology will develop recurrence. Reverse-transcriptase PCR (RT-PCR) is a highly sensitive method for detection of lymph-node micrometastases, but a ccurate quantitative assessment has been difficult. Methods We studied primary tumours and 156 lymph nodes from 32 patients wit h cervical cancer (stage IA2, IB1, and 1B2) and 32 lymph nodes from nine pa tients with benign disease. A fully quantitative, real-time RT-PCR assay wa s used to document absolute copy numbers of the epithelial marker cytokerat in 19. Primers and probe were designed not to amplify either of the two cyt okeratin 19 pseudogenes. Findings All primary tumours and histologically involved lymph nodes (six) had more than 10(6) copies of cytokeratin 19 mRNA per mug total RNA. Expres sion of cytokeratin 19 (up to 1.1x10(5) copies per mug RNA) was detected in 66 (44%) of 150 histologically uninvolved lymph nodes, and in nodes from 1 6 of 32 patients with cervical cancer. 15 of these 16 patients with evidenc e of micrometastases had the highest cytokeratin 19 transcription level in a first lymph-node drainage-station (three obturator, six internal, and six external iliac node). Transcription of cytokeratin 19 was found at a low l evel in just one of 32 lymph nodes obtained from nine patients with benign disease. Median copy number of cytokeratin 19 transcription was significant ly higher (>10(3) copies) in association with adverse prognostic features. Interpretation The results suggest that about 50% of early-stage cervical c ancers shed tumour cells to the pelvic lymph nodes. The amount of cytokerat in 19 expression was related to clinicopathological features. Further studi es are required to document the clinical implications of molecular micromet astases.