Abstract
BackgroundRecently, especially in Japan, several researchers have suggested that colorectal cancer can develop not only through an adenoma-carcinoma sequence but also from normal mucosa via a de novo pathway, and that these de novo cancers have more aggressive malignant potential. We report a case of aggressive colon cancer resulting in systemic metastasis despite small tumour size.Case PresentationA 35-year-old woman presented at the referring hospital with swelling of the left cervical lymph node. Biopsy of the lymph node revealed metastatic adenocarcinoma; however, CT scan and mammography were unable to identify the site of the primary lesion. She was diagnosed with unknown primary cancer and referred to our hospital for further examination. Immunohistochemical reevaluation showed the cervical lymph node biopsy specimen to be positive for CDX2 and CK20 and negative for CK7 expression, leading us to suspect the presence of a primary colorectal cancer. We performed a total colonoscopy, and detected a small protruding lesion in the transverse colon. The tumour was only 12 mm in diameter, with a central depressed component and a severely thickened stalk, which suggested direct cancer invasion of the deep submucosa. We concluded that this lesion was the site of origin of the metastasis despite the small tumour size, and performed diagnostic endoscopic mucosal resection. The lesion was found to have an intramucosal cancer component, demonstrating that this lesion represented primary colon cancer. The patient was referred to the gastrointestinal oncology division for systemic chemotherapy.ConclusionsIn this case, immunohistochemical findings strongly suggested the existence of a colorectal cancer. The non-polypoid gross appearance of the tumour suggested that it can originate de novo , thus providing a valuable case in support of the aggressive malignant potential of a de novo colorectal cancer pathway.
Highlights
Especially in Japan, several researchers have suggested that colorectal cancer can develop through an adenoma-carcinoma sequence and from normal mucosa via a de novo pathway, and that these de novo cancers have more aggressive malignant potential
In this case, immunohistochemical findings strongly suggested the existence of a colorectal cancer
Immunohistochemistry (IHC) studies showed the biopsy specimen to be negative for cytokeratin 7 (CK7), and positive for CDX2, an intestine-specific homeobox transcription factor, and cytokeratin 20 (CK20), a cytoskeletal protein usually found in the colonic epithelium
Summary
In patients with an unknown primary carcinoma, the site remains unidentified in 15~25% of the cases even after autopsy [11,12], recent advances in clinical examination and diagnostic work-up have decreased this frequency. The median survival of high-risk patients with cancer of unknown primary origin ranges from 3 to 11 months, making prompt diagnosis and treatment very important [13,14,15] In this case, 2 months elapsed between the initial consultation at the referring institution and the patient’s presentation at our hospital. De novo cancers are thought to have an aggressive growth phenotype, despite small tumour size, and to quickly infiltrate neighbouring tissue and lymph nodes In this case, the tumour exhibited a severely thickened stalk, which suggested direct cancer invasion of the deep submucosa, and a clearly demarcated depressed area in the centre of the lesion, suggesting that it can originate de. Competing interests The authors declare that they have no competing interests
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