Figure 13.

A pancreatic ductal adenocarcinoma metastatic to the lung exhibiting a lepidic pattern (A, at a low-power magnification & B, at a high-power magnification), focal CK7 expression (C), negative TTF1 (D), diffuse weak CDX2 expression (E), and loss of SMAD4 (F). Of note, strong nuclear expression of TTF1 in the entrapped pneumocytes may give a false positive impression. Also, loss of SMAD4 expression has been reported as useful marker for the diagnosis of pancreatic adenocarcinoma, but a significant proportion of invasive mucinous adenocarcinomas of the lung harbors this alteration.¹³⁸