The incidence and clinical significance of lymph node micrometastases determined by immunohistochemical staining in stage I - lymph node negative endometrial cancer

Objective: Determine the incidence and clinical relevance of lymph node micrometastases found with immunohistochemical (IHC) staining in patients diagnosed with stage I lymph node-negative endometrial adenocarcinoma. Methods: Eligible patients with endometrioid-type histology and negative lymph nodes by H&E were identified by a computerized database. After histologic confirmation, all paraffin-embedded pathologic specimens were freshly sliced and stained with IHC stains for pancytokeratin. Slides were interpreted by two pathologists and positive IHC staining for micrometastases was defined as positive staining of cells <2 mm in greatest dimension. Patient demographics, clinicopathologic factors, and follow-up data were abstracted. Results: Fifty-one patients were included in our study. Most patients had stage IA (84%) tumors of grade 2/3 histology (51%), and 11 patients (22%) received adjuvant therapy. Mean number of lymph nodes was 12.2 per patient. Of 151 lymph node paraffin blocks evaluated for pancytokeratin, only two (1.3%) had IHC-positive micrometastases. The two lymph node-positive results occurred in separate patients, leading to 3.9% of all patients in our cohort. Both micrometastatic lymph node-positive patients had adjuvant radiation therapy for uterine high-risk factors and are currently without evidence of disease at 15 and 16 months, respectively. Three lymph node-negative patients (6.1%) have developed recurrences within a median follow-up of 15 months. Conclusion: The incidence of IHC stain-positive micrometastases in H&E-negative lymph nodes is low in surgically staged endometrial cancer and does not justify routine IHC staining. Additionally, as little evidence exists to support the clinical significance of IHC-stained micrometastases in endometrial cancer, further study is warranted.