Figure 3

Histological examination of the pituitary lesion surgically removed. A: Primary site of disease (colorectal tissue; hematoxylin-eosin stain). B: Adenohypophyseal parenchimal tissue with evidence of metastatic cells from adenocarcinoma. On the left side: Adenohypophyseal tissue; On the right side: Clusters of neoplastic glandular cells (hematoxylin-eosin stain). C: Metastatic adenocarcinomatous cells invading adenohypophyseal parenchimal tissue. No evidence of immunocoloration for CDX-2 (caudal type homebox transcription factor 2) into adenohypophyseal parenchimal tissue (upper right corner of the image); positive nuclear CDX-2 immunocoloration found in clusters of metastatic adenocarcinoma cells agreeing with the rectal origin of the lesion. D: Metastatic adenocarcinomatous cells invading adenohypophyseal parenchimal tissue. No evidence of immunocoloration for cytokeratin 20 into adenohypophyseal tissue; positive cytokeratin 20 immunocoloration found in clusters of metastatic adenocarcinomatous cells.