Possible metaplastic origin of lymph node "metastases" in serous ovarian tumor of low malignant potential (borderline serous tumor).

A patient with a stage III serous ovarian carcinoma of low malignant potential (borderline serous tumor) is described who had extensive involvement of the pelvic and para-aortic lymph nodes by both borderline tumor and endosalpingiosis. Transition from endosalpingiosis to papillary serous borderline tumor was demonstrable in multiple intranodal sites, and in fully developed lesions, areas of metaplastic growth acquired a desmoplastic stroma. This finding suggests that the lymph node "metastases" may have arisen de novo by neoplastic transformation of preexistent metaplastic tubal-type epithelium (endosalpingiosis), and would lend further credence to the metaplastic (rather than metastatic) origin or extraovarian implants in serous ovarian carcinoma of low malignant potential.