A solitary inguinal lymph node metastasis from a poorly differentiated adenosquamous cell carcinoma of unknown origin in a 52-year-old female is described. The patient was reported to have had a 2-cm palpable mass in the left inguinal area for three years. She had made regular annual clinic visits for Pap smears since the age of 45 years. Her last visit was eight months prior to a complaint of progressive abdominal distention and dull pain of three months' duration. Physical examination showed a huge pelvic mass, and ultrasound and magnetic resonance imaging of the abdomen showed a 12-cm complex solid mass on the left ovary. The patient underwent a complete excisional biopsy of the left inguinal lymph node. Frozen section pathology revealed a poorly differentiated adenosquamous cell carcinoma. Exploratory laparotomy immediately followed pathologic confirmation of malignancy of the left inguinal lymph node. Complete surgical staging including abdominal cytology, total abdominal hysterectomy, bilateral salpingo-oophorectomy, infracolic omentectomy, retroperitoneal lymph node sampling and excisional biopsy was performed for all suspicious lesions. Stage IIIC malignant mixed mesodermal tumor (MMMT) was diagnosed due to positive left inguinal lymph node metastasis. However, the retroperitoneal lymph node and intra-abdominal cavity did not show spread of the tumors, except those confined to the left ovary with adhesion to the cul-de-sac, and sole lymph node metastasis in a left inguinal lymph node. Although we could not prove that the left inguinal lymph node metastasis had been present for the three years that it was palpable without histologic confirmation, we believe that any enlarged inguinal lymph node might be the first hint of underlying malignancy in the pelvic area, lower extremities or perineal area. In cases of a poorly differentiated carcinoma of inguinal lymph nodes of unknown origin, the abdomen should be carefully evaluated.