Prospective assessment of histological serial sectioning of pelvic lymph nodes in prostate cancer: a cost-benefit analysis

What's known on the subject? and What does the study add? Metastatic spread to the regional lymph nodes (LNs) is the single worst predictor of survival in prostate cancer. Knowledge of the LN status is crucial, as the treatment strategy is substantially altered in non-organ-confined disease. Current routine pathological protocols for evaluation of LN resection specimens do not demand a minimum of cross-sections per LN to be examined. Depending on the LN size, usually one to two sections are examined. This might lead to underestimation of the true metastatic burden. The present study shows that additional examination of cross-sections in pelvic LNs and applying prostate cancer-specific cytokeratine immunostaining does not lead to significantly increased detection of prostate cancer metastases. However, the work-load and the expenses were significantly higher compared with routine evaluation.

Objective: To evaluate the diagnostic gain in the detection of lymph node (LN) metastases of prostate cancer and the additional expenses of histological step-section analysis, including immunohistochemistry compared with routine histopathological evaluation.

Patients and methods: In a prospective study, 19 patients with prostate cancer at high risk of LN metastases (>cT2c and/or PSA level of >20 ng/mL and/or Gleason score >8) underwent sentinel-guided LN resection. All palpable LNs were submitted to step-section analysis in 200-µm sections and concomitant immunohistochemical staining for cytokeratine (AE1/AE3), in addition to routine histopathology of one or two haematoxylin and eosin-stained sections per LN. The number of positive LNs and LN-positive patients for each method was compared; additional expenses in labour time and material for the extended evaluation were estimated.

Results: In all, 413 LNs were resected; 220 LNs were palpable and were included in the study. In seven of the 19 patients routine histopathological evaluation revealed LN metastases in 24 of 220 LNs (10.9%). Extended LN evaluation with step sectioning and cytokeratin immunohistochemistry did not reveal any additional patients with LN metastases. In one patient already diagnosed with LN metastases on routine histology, four additional LN metastases were detected upon extended LN evaluation. Three LNs of two patients, one of them pN0, contained disseminated tumour cells. Compared with conventional histological evaluation, serial-section analysis and immunohistochemistry increased expenses in materials and labour time 18.7-fold.

Conclusions: Serial-section analysis seems to have only a minimal diagnostic gain; however, valid conclusions cannot be drawn, as not all LNs were submitted to extended evaluation. Considering the additional expenses, extensive LN evaluation in prostate cancer cannot generally be recommended.