Occult Lymph Node Metastases Detected by Cytokeratin Immunohistochemistry Predict Recurrence in Node-negative Endometrial Cancer

Objective: Even after curative resection of early endometrial cancer, some patients die as a result of recurrence. We believe that these patients likely had occult lymph node metastases at the time of diagnosis. In an attempt to identify the responsible occult metastases, the clinicopathological significance of cytokeratin expression in lymph nodes with unconfirmed metastasis was evaluated retrospectively in patients with endometrial carcinoma.

Methods: We examined 304 pelvic lymph nodes and 46 primary tumors excised from 46 patients with endometrial cancer, including 36 with Stage I disease and 10 with Stage IIIc disease. Formalin-fixed paraffin-embedded tissue sections were stained immunohistochemically using antibodies against cytokeratin, CA125, and macrophage-related antigen. Sections were also stained with hematoxylin and eosin.

Results: In 10 patients with Stage IIIc disease, cytokeratin expression was detected in cells other than the tumor cells in all 13 lymph nodes with metastasis and also in 20 (30.3%) of 66 lymph nodes without metastasis. Cytokeratin expression was observed in 37 (16.4%) of 225 lymph nodes with unconfirmed metastasis, which were obtained from 14 of 36 patients with Stage I disease. Five of fourteen patients with lymph nodes expressing cytokeratin had recurrent disease in the pelvic cavity, while all 22 patients with unconfirmed cytokeratin expression in their lymph nodes showed no recurrence. Cytokeratin and CA125 were detected simultaneously on macrophages in lymph nodes. Cytokeratin expression in lymph nodes was closely related to lymph-vascular space involvement of the primary tumor, but was not related to either histological grade or depth of myometrial invasion. Multivariate analysis identified cytokeratin expression as an independent risk factor for recurrence in Stage I endometrial cancer.

Conclusions: The immunohistochemical expression of cytokeratin in lymph nodes with undetected metastases predicts occult metastasis to these nodes and is a risk factor for recurrence in early-stage endometrial cancer.