(18)F-fluorodeoxyglucose positron emission tomography/computed tomography-positive lymph node endometriosis masquerading as lymph node metastasis of a malignant tumor.

Endometriosis is defined as the presence of endometrium-like tissues at extrauterine sites, most commonly in the abdominal cavity. Lymph node endometriosis is a rare but clinically important type of endometriosis that can mimic lymph node metastasis of a malignant tumor. (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) is a useful tool for diagnosing malignant tumors, although it occasionally shows false positive results in tissues with high metabolic activity caused by severe inflammation. In the present report, we describe a case of lymph node endometriosis that mimicked lymph node metastasis of a malignant tumor and showed a positive result on (18)F-FDG PET/CT. The findings of the present case suggest that lymph node endometriosis could present as swollen lymph nodes with (18)F-FDG PET/CT-positive results and provide important information for determining an appropriate treatment strategy.