Detection of Sentinel Node Micrometastasis by Step Section and Immunohistochemistry in Patients With Prostate Cancer

Purpose

The role of step section and immunohistochemistry for diagnosing sentinel node micrometastases and the sentinel node concept in patients with prostate cancer was investigated. In patients administered neoadjuvant hormone therapy its influence on the sentinel node concept and metastasis diagnosis was also investigated.

Materials and Methods

Of 62 patients without metastasis enrolled in our study 42 were eligible for analysis. The prostate was injected with the radioactive tracer ^99mtechnetium phytate 5 to 6 hours before surgery. A planar image and a fusion image with x-ray computerized tomography and single photon emission computerized tomography were obtained 3 hours after tracer injection. Extended lymph node dissection and lymphatic mapping were performed to verify the sentinel node concept. Lymph node metastasis was histologically confirmed by routine hematoxylin and eosin, and thereafter by immunohistochemistry using 250 μm step-sectioned slides.

Results

The mean number of dissected lymph nodes was 26.3 per patient. Hot nodes were noted in 41 of 42 patients. The sensitivity and specificity of hot node prediction of lymph node metastasis were 92.3% and 100%, respectively. On routine hematoxylin and eosin examination lymph node metastases were found in 4 of 27 patients with and in 4 of 15 without neoadjuvant hormone therapy. Step section and immunohistochemistry identified micrometastasis in 5 more patients with neoadjuvant hormone therapy.

Conclusions

The validity of the sentinel node concept in conjunction with the detection of micrometastases was considered to be high. Furthermore, it was suggested that the efficacy of metastasis diagnosis may also be enhanced, especially in patients receiving neoadjuvant hormone therapy.

Key Words: prostate, lymph nodes, prostatic neoplasms, radionuclide imaging, neoplasm metastasis

Abbreviations and Acronyms: CT, computerized tomography, IHC, immunohistochemistry, LN, lymph node, NHT, neoadjuvant hormone therapy, PSA, prostate specific antigen, SN, sentinel node, SPECT, single photon emission CT