Infiltrating adenocarcinoma arising in a villous adenoma of the anal canal

Figure 1 Microscopic sections. A: The adenoma demonstrate villous architecture with long, delicate fronds (HE, × 40); B: The villous fronds are lined by dysplastic, intestinal-type epithelium with frequent goblet cells (HE, × 100); C and D: Multiple foci of invasive carcinoma are identified, with invasion confined to the lamina propria (HE, × 100).

Figure 2 Intraoperative photographs. A and D: Very large hemorrhoids up to 2 cm circumferentially located around the anal canal; B: The final appearance after complete excision of the hemorrhoids and the malignant mass; C: The area that contained the adenocarcinoma, previously excised in the emergency department, and prior to operating room excision.

Figure 3 Immunohistochemical staining. A: Cytokeratin 20 is diffusely positive within the epithelium (× 100); B: Cytokeratin 7 is negative (× 100).