Colon cancer is one of the most common cancers. In one postmartum study, only 0.8% of colon cancer metastasized to the stomach . Herein, we present an interesting case of colon cancer with gastric metastasis.
A 68 year old lady presented in mid 2008, with a 1 month history of alternating diarrhea and constipation, weakness and crampy abdominal pain. Further diagnostic evaluation confirmed a diagnosis of a high risk, stage II, carcinoma of the colon . After resection of primary lesion, she received 12 cycles of adjuvant chemotherapy with FOLFOX.
She underwent a laparoscopic sigmoidectomy in 2006 showing an infiltrating moderately differentiated adenocarcinoma 4 cm extending through the muscularis propria into the pericolonic adipose tissue with perineural invasion but no lymph nodes involved. It was staged T3N0. Due to high risk features she was offered adjuvant chemotherapy with FOLFOX which she received then underwent observation. Multiple colonoscopies and scans were negative until a CT scan in June 2010 showed a gastric mass suggesting metastases. She had an upper endoscopy showing a large fungating mass in the fundus of the stomach (Figure 1) which was biopsied and positive for adenocarcinoma with the immunohistochemical profile favoring metastasis from the previously known colorectal cancer. The mass was seen to extend to the muscularis propria (Figire 2). She was started on chemotherapy with Irinotecan and 5-FU in 2010 with partial response. She developed bleeding from the gastric mass. Due to lack of any other foci of metastases and because of the bleeding, the patient underwent partial gastrectomy. Surgical pathology showed metastatic colon cancer to stomach, completely excised, with clean margins. Fifteen months later the patient had no endoscopic or radiographic evidence of cancer.
Colon cancer is the third most common cancer diagnosed in men and the second in women. The incidence and mortality of colorectal cancer are estimated to be the highest in African Americans . Approximately 142,820 new cases of large bowel cancer are diagnosed each year, of which 102,480 are colon and the remainder are rectal cancers .
The incidence of colorectal cancer varies over 10-fold. The highest incidence rates are in Australia and New Zealand, Europe and North America, and the lowest rates are found in Africa and South-Central Asia. In the United States, both the incidence and mortality have been slowly but steadily decreasing    . The difference in incidence rates is attributable to the differences in dietary and environmental factors .
The major risk factors that increase the risk of colon cancer include hereditary forms of colorectal cancer, age, a personal or family history of sporadic colorectal and inflammatory bowel disease. Several potentially modifiable risk factors including obesity and lack of physical activity have been consistently identified in observational studies .
Colorectal cancer can spread by lymphatic and hematogenous dissemination, as well as by contiguous and transperitoneal routes. The most common sites of metastasis are the regional lymph nodes, liver, lungs, and peritoneum .
The first site of hematogenous spread is the liver followed by the lungs, bone and many other sites. This is due to that the venous drainage of the intestinal tract is via the portal system. Due to the venous drainage of the lower rectum, tumors metastasize to the lungs because the inferior rectal vein drains into the inferior vena cava rather than into the portal venous system .
The involvement of the stomach by metastases is rare with the most common primary sites include melanoma, breast and lung carcinoma. Gastric metastasis from colon cancer has been reported infrequently .
The endoscopic appearance of gastric metastases is variable. Gastric involvement may be characterized by a single lesion or by multiple lesions. Often the lesion appears as a "volcano-like" ulcer. The metastases may have the clinical appearance of a primary stromal gastric tumor. Metastasis to the stomach can be mistaken for a primary gastric cancer; this happens when the primary site is not present at the time of finding a gastric lesion .
As instance, adenocarcinoma of gastrointestinal or pancreatobiliary origin that metastasize to the stomach may still look like a primary gastric cancer if preservation of the morphology of gastric glands and pits is maintained. Similarly, metastatic cancer from the breast may initiate desmoplasia within the stomach so as to simulate linitisplastica .
The treatment of colon cancer depends on the staging of colon cancer which includes systemic chemotherapy using 5-Fluorouracil which is considered the backbone of chemotherapy regimens, both in the adjuvant and metastatic tumors .
While radiation therapy remains a standard modality for patients with rectal cancer, the role of radiation therapy is limited in colon cancer. It does not have a role in the adjuvant setting, and in metastatic settings, it is limited to palliative therapy for selected metastatic sites such as bone or brain metastases .
Surgery is the only curative modality for localized colon cancer and potentially with limited metastasis to the liver and or lung. The decision for deciding which surgical approach depends on the location of the tumor within colon The general principles for all operations include removal of the primary tumor with adequate margins and lymphatic dissection .
Palliative surgery is not curative and it is done to a symptomatic patient with advanced disease to prevent bleeding, obstruction and symptoms related to the cancer. The aim is to improve the patient’s quality of life .
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