High-grade serous cancer of undetermined primary origin presenting as solitary inguinal lymph node enlargement

A 62-year-old woman presented with unilateral inguinal lymphadenopathy, existing for several months. As it was initially thought to be lymphoma, the lymph node was resected. Pathology, however, revealed a metastasis of a high-grade papillary serous cancer, according to its stainings, most likely ovarian in origin. Further staging showed lymphadenopathies in the inguinofemoral, para-aortic and mediastinal regions. Consequently, the multidisciplinary oncologic meeting advised a diagnostic laparoscopy which showed no macroscopic spread within the abdomen. Pathological examination of biopsies as well as both ovaries showed no sign of ovarian cancer. The patient received standard chemotherapy, that is, carbo-Taxol-Avastin, to which she showed complete response after three cycles as shown on positron emission tomography–CT. A review of existing literature showed that this is a very unusual case of high-grade serous carcinoma, where no site of origin could be found.