Metastases and Mimics of Colorectal Carcinoma.

Secondary involvement of the colon by other malignant neoplasms may mimic primary colorectal carcinoma and results from direct extension, peritoneal seeding, or hematogenous spread. Careful gross examination and key histologic features may suggest the presence of a metastasis. Most primary tumors are solitary mucosa-based lesions, whereas secondary neoplasms may be multiple and often substantially affect the outer colonic wall. Primary colorectal cancers are comprised of malignant cribriform glands with necrosis and show dysplasia in the overlying mucosa, whereas secondary tumors show variable growth patterns and readily detectable lymphovascular invasion. Several benign processes, namely diverticulitis and intestinal endometriosis, may also mimic colon cancers and their nature may not be apparent prior to surgical intervention. [ABSTRACT FROM AUTHOR]