AdenoCA of Colon : Mucinous
Mucinous variant makes up 10% of all colorectal carcinomas. It is characterized by large collections of extracellular mucin (MUC2 type) comprising at least 50% of the tumor. The glandular component is usually well-differentiated and consists of irregular, branching or anastomosing glands lined by tall columnar epithelium with minimal cytologic atypia and low mitotic activity. The presence of mucin in the stroma incites a strong desmoplastic and inflammatory response. Some areas of tumor consist only of pools of dissecting mucin containing inflammatory infiltrate. At molecular level, they show defective DNA mismatch repair resulting in high microsatellite instability (MSI). They usually present at more advanced stage due to their tendency to invade adjacent structures, develop peritoneal implants, and produce lymph node metastases. In this image, the tumor cells are arranged in clusters and small glandular structures in the submucosa surrounded by pools of mucin. The overlying mucosa is hyperplastic.