A Case of a Medullary–Type Poorly Differentiated Adenocarcinoma of the Transverse Colon Diagnosed with Perforation

Abstract

An 80–year–old man who had undergone surgery for gastric cancer about 20 years previously had metastasis of poorly differentiated adenocarcinoma in the left supraclavicular lymph nodes. CT showed multiple lymph node metastases in the right upper abdomen and hepatocellular carcinoma, but showed no other lesions suspected of malignancy. Findings of histopathology with immunohistochemical staining of the metastatic lymph node biopsy and CT revealed recurrence of gastric cancer. Chemotherapy for gastric cancer markedly reduced the metastatic lymph nodes. Approximately 8 months after the treatment initiation, partial resection of the colon was performed for the transverse colon perforation. Because a perforated poorly differentiated adenocarcinoma which invaded the subserosa was detected in the resected specimen, we reexamined to identify the primary site of metastasis to the lymph nodes with immunohistochemical staining. Based on the findings, the patient was finally diagnosed as having lymph node metastasis from a medullary–type colonic adenocarcinoma with the expression of CK7+/CK20－/CDX2− and a mismatch repair deficiency.