A cancer of unknown primary showing positive immunoreactions for intestinal epithelial markers

Abstract

Cancer of unknown primary is defined in cases in which cancer cells are found in the body, but the place where the cells first started growing (the origin or primary site) cannot be determined. We herein present a case of cancer of unknown primary which showed positive reactions for intestinal markers by immunohistochemistry and was sensitive to a standard chemotherapeutic regimen used for colon cancer, FOLFOX. A 74-year-old female was admitted to Asahikawa Medical University Hospital with lower abdominal pain. She had a past history of a total abdominal hysterectomy with bilateral salpingo-oophorectomy in 1990 due to a cervical squamous cell carcinoma in situ of the uterus. At the present admission, an elastic hard tumor was palpable on the right side of her abdomen. A blood examination showed normocytic normochromic anemia, a low level of serum albumin and high levels of blood urea nitrogen and serum creatinine. Computed tomography revealed carcinomatous peritonitis, but no abnormal findings in the liver, pancreas, spleen, kidneys, lungs, mediastinum or intestines. Gastroduodenoscopy and sigmoidoscopy showed no abnormal findings. Total colonoscopy could not be performed because of the presence of severe adhesions from the previous total abdominal hysterectomy with bilateral salpingo-oophorectomy. Positron emission tomography detected no abnormal accumulations. The histological findings of biopsy specimens obtained by open biopsy showed poorly differentiated adenocarcinoma. The cancer cells showed positive immunoreactivities for cytokeratin (CK) 20, caudal-related homeobox 2 (CDX-2), CEA and p53, negative staining for CK7 and weakly positive staining for CA125, suggesting that the cancer had originated from the intestine. Based on the clinical and histological findings, the cancer was thought to have originated in the colon. The patient was treated with FOLFOX. After five courses of FOLFOX, the abdominal symptoms disappeared and the ascites was markedly decreased. The patient died due to a cerebral infarction during the seventh course of FOLFOX. While this case suggests the usefulness of an immunohistochemical analysis for predicting the origin of tumors, a novel genomic analysis is another feasible option to determine the origin of the cancer in such cases.