PMC

Histology of medullary carcinoma of the pancreas. The tumor has a syncytial growth pattern of the cells.

K-ras sequencing of codon 12 of a medullary carcinoma (A) and a poorly differentiated conventional adenocarcinoma (B). The medullary carcinoma has a wild-type K-ras gene, but the conventional adenocarcinoma has a GGT (gly) to GAT (asp) mutation.

Immunohistochemistry for DNA repair-gene products in medullary carcinomas of the pancreas. A: This medullary carcinoma has intact nuclear labeling for the MSH2 gene product. B: Another medullary carcinoma has no expression of Mlh1. Note that the nuclei of stromal cells do express Mlh1.

Histology of the Mlh1-deficient pancreatic (A) and colonic (B) carcinomas from the patient presumed to have HNPCC. Both carcinomas had MSI, and both had wild-type K-ras genes. Note that the histological patterns of the two cases are different: the pancreas has the medullary phenotype, whereas the colon cancer is gland-forming.

Histology of a medullary carcinoma of the pancreas with lymphoepithelioma-like features. A: The neoplasm has the characteristics of medullary carcinoma with the additional finding of an intense intratumoral lymphocytic infiltrate. B: In situ hybridization for Epstein-Barr virus-encoded RNA-1 is positive in the nuclei of the neoplastic cells.

BAT 25 and BAT 26 PCR products for two medullary carcinomas, a conventional adenocarcinoma, and normal pancreas. For both the BAT 25 and BAT 26 PCR products: lane 1, pancreatic medullary carcinoma with a microsatellite shift; lane 2, normal pancreas from the same patient; lane 3, a different pancreatic medullary carcinoma without a shift; and lane 4, a conventional ductal adenocarcinoma without a shift. The shifting medullary carcinoma and the normal pancreas are both from the patient with synchronous pancreatic and colonic carcinomas.