Colorectal Adenocarcinoma

Radiologic-Pathologic Correlation

Abstract Introduction Etiologic and Growth Characteristics

Tumor Spread and Staging Role of Radiology Treatment and Follow-Up Prognosis

Conclusion Source Information References

Tumor Spread and Staging

Unlike cancers in other areas of the gastrointestinal tract, there is no significant difference between colon carcinoma in situ (defined as a cancer still confined to the epithelium) and intramucosal colon carcinoma (including lesions that extend into the lamina propria). Because there are no lymphatics in the lamina propria, a carcinoma confined to the mucosa will not metastasize. Therefore, in the colon, the adenocarcinoma is not considered invasive until it has penetrated through the muscularis mucosa into the submucosa or the successively deeper layers of the muscularis propria or serosa (5). Beyond the serosa, it may extend into the peritoneal cavity or involve neighboring structures.

Once carcinoma extends into the submucosa, it has access to local lymphatic channels, and the risk of the lymphatic invasion increases with increasing depth of disease. This eventually leads to the spread of carcinoma to regional lymph nodes. The lymph node channels affected are determined by the location of the primary carcinoma. In most cases, there is a predictable progression of drainage into the surrounding lymph node chains from the pericolic lymph nodes to nodes along the course of the larger, named vascular trunks. The more lymph nodes affected, the lower the chance of 5-year survival.

Invasion of cancer into the peritoneal cavity is usually associated with poorly differentiated carcinomas. However, peritoneal metastasis from low-grade adenocarcinoma of the colon occurs and is an uncommon (<5% of cases) cause of pseudomyxoma peritonei, an entity usually caused by low-grade neoplasms of the appendix and ovary (Figure 7) (27).

Distant metastases are usually seen in the liver (75% of cases), but they may occur in the lung (5%-50%), adrenal gland (14%), ovary (3%-8%), bone (5%), brain (5%), and mesentery (10%) (14,28). Distant metastatic disease may occur through lymphatic extension or hematogenous venous spread.

The liver is the most common site of distant metastatic disease from colon carcinoma due to the portal venous drainage of the colon. Carcinomas of the rectum, however, have dual venous drainage into both the portal and systematic venous systems. Therefore, rectal carcinomas may manifest with hematogenously disseminated disease elsewhere (eg, in the lung) without associated liver metastases. Otherwise, it is unusual to have more distant metastatic disease without associated disease in the liver.

Ovarian metastases from adenocarcinoma of the colon are often called Krukenberg tumors. Although this term was originally used to describe a particular histologic appearance of sarcomatous stroma with mucin-containing signet-ring cells, it is now applied more broadly to include any metastases to the ovary, particularly those arising from the gastrointestinal tract (29). Ovarian metastases from primary colon cancer are now the most common, occurring more than twice as often as those arising from primary gastric cancer (29). In general, premenopausal women with advanced disease are most likely to be affected, and bilateral oophorectomy is often performed prophylactically at the time of colon resection (29).

There have been so many staging classifications for colorectal carcinoma that the subject can be both confusing and intimidating. The original Dukes classification of 1932 described the staging of rectal carcinoma only and was divided into three simple stages: A, disease limited to the rectum; B, disease that extended outside the rectum; and C, disease with associated adenopathy. However, numerous modifications of this staging system followed. The most popular is the Astler-Coller classification or the so-called modified Dukes classification (Table 1) (23). Although this system has Dukes in its name, it has little resemblance to the original Dukes classification, except for the fact that they both use letters in describing different stages of disease. The most significant addition to all staging systems, including the original Dukes and the Astler-Coller classifications, came in 1967 with the addition of a stage D, which incorporated distant metastatic disease (30).

Although prognosis and treatment decisions are often made in reference to the modified Dukes classification, the tumors are probably better defined according to the TNM classification (Table 2) (31). The TNM classification offers a systematic evaluation of the primary tumor site (T), regional lymph nodes (N), and distant metastases (M). Stages I-III roughly parallel the original Dukes classification. Stage IV corresponds to stage D or distant metastatic disease. The rates for 5-year survival decrease with increasing stage of cancer.

Abstract Introduction Etiologic and Growth Characteristics

Tumor Spread and Staging Role of Radiology Treatment and Follow-Up Prognosis

Conclusion Source Information References