Synchronous Undifferentiated and Medullary Carcinomas of the Colon; Recurrence of Undifferentiated Colonic Carcinoma in the Peripancreatic Retroperitoneum

In the World Health Organization 2010 classification, undifferentiated carcinoma of the colon has been subclassified separately from medullary carcinoma of the colon. It is a rare colorectal malignancy with inconsistent histological features and lack of morphological, immunohistochemical, and molecular evidence of differentiation. Some of these tumors have microsatellite instability (MSI). The tumor has infiltrative borders and …