Unknown Primary Cancer with Ileocecal Lymph Node Metastasis—A Case Report—

Abstract

A 72-year-old man came to our hospital because of right lower abdominal pain. Abdominal computerized tomography (CT) scan revealed ileocecal lymph node enlargement, but otherwise we could not find apparent primary lesion. The lymph node tended to enlarge with time. Positron emission tomography (PET)-CT scan also suggested a malignancy at the same site. Thus, we diagnosed the case as unknown primary cancer with ileocecal lymph node metastasis. He underwent laparoscopic ileocecal resection. Histopathologically, adenocarcinoma containing mucinous adenocarcinoma with metastasis to the resected lymph nodes was confirmed, but no primary cancer was found in the resected intestinal specimen. Immunohistochemistry revealed the nodes to be positive for caudal-related homeobox transcription factor (CDX) 2, but negative for cytokeratin (CK) 7 and CK 20. Furthermore, immunohistochemical stainings of mucin (MUC) 1, 2, AC and 6 for mucinous adenocarcinoma were positive. We thus suspected digestive tract cancer, hepatobiliary and pancreatic cancer, or a urological tumor. Even after the operation, the primary cancer was still unknown by capsule endoscopy, magnetic resonance cholangiopancreatography (MRCP), magnetic resonance imaging (MRI) and cystoscopy. Follow-up observation without adjuvant chemotherapy was provided. The p53 antibody levels which had elevated before surgery were immediately normalized after the surgery. Although three years have passed since the surgery, no recurrence has been detected. In this case, long-term survival could be achieved with surgery alone. It is so rare that further accumulation of clinical cases, including our case, would be needed.