Recent Developments on the Significance and Pathogenesis of Lymph Node Involvement in Ovarian Serous Tumors of Low Malignant Potential (Borderline Tumors)

In approximately 27% of patients that were surgically staged for ovarian serous borderline tumors (ovarian serous tumors of low malignant potential), regional lymph nodes, most commonly the pelvic and paraaortic groups, display morphologically similar epithelial clusters. Lymph nodes above the diaphragm may also be involved. Lymph node involvement does not adversely impact the overall survival of patients with ovarian serous borderline tumors, but there is controversy as to whether this finding is associated with a decrease in recurrence-free survival. Nodular aggregates of epithelium greater than 1 mm in maximum dimension, as compared with all other patterns of nodal involvement, have been associated with reduced recurrence-free survival. The lymph nodes may also be the site of recurrence and/or progression to carcinoma of an ovarian serous borderline tumor. Recent molecular and morphologic data suggest that although most nodal implants are indeed metastatic from their synchronous ovarian neoplasms, a small subset arise de novo from nodal endosalpingiosis. The precise mechanistic basis for how these noninvasive neoplasms achieve nodal metastases is unclear. However, because most patients with nodal metastases also have peritoneal implants, tumors that are ovary-confined and without ovarian surface involvement are rarely associated with nodal involvement, microinvasive borderline tumors frequently display lymphatic vessel involvement yet show a remarkably low frequency of nodal involvement, in conjunction with the recent finding that node-positive and node-negative tumors display no significant differences in lymphatic vessel density, suggest that the route of spread to lymph nodes in most cases is via the peritoneal and not tumoral lymphatics.