Rare histological subtype of invasive micropapillary carcinoma in the ampulla of Vater: A case report

Figure 1 Macroscopic appearance. A: Macroscopic appearance of the resected specimen showing an irregular papillary surface at the enlarged papilla of Vater measuring 23 mm × 10 mm. The tumor is seen extending into the dilated ampullary channel with an exophytic growth pattern; B: The cut surface of the tumor is grey to white in color.

Figure 2 Microscopic findings. A: The section shows that the surface of the tumor is composed of tubulo-papillary proliferation [hematoxylin and eosin (H&E) stain, magnification 40 ×]; B: Significant architectural and nuclear atypia, including loss of polarity (H&E stain, magnification 200 ×); C: Transition from the tubular structure to the invasive micropapillary pattern (H&E stain, magnification 40 ×); D: The invasion edge of the tumor composed of moderately differentiated adenocarcinoma and micropapillary carcinoma (H&E stain, magnification 200 ×); E: Neutrophilic infiltration forming intraepithelial microabscesses in the tumor nest (H&E stain, magnification 400 ×).

Figure 3 Immunohistochemical findings. A and B: Immunohistochemical staining for CK7 revealing positivity in both tubular and micropapillary carcinoma (immunostain, magnification 200 ×); C and D: Tumor cells in both tubular and micropapillary portions showing positivity for caudal-related homeobox transcription factor-2 (immunostain, magnification 200 ×); E: Tumor cells on the surface area showing positivity for CK20 (immunostain, magnification 200 ×); F: The micropapillary component showing focally positivity for mucin1 (immunostain, magnification 400 ×). CDX2: Caudal-related homeobox transcription factor-2; MUC1: Mucin1.

Figure 4 Changes in carcinoembryonic antigen and carbohydrate antigen 19-9 serum levels from the perioperative period to the last follow-up. Serum tumor marker levels of carcinoembryonic antigen gradually elevated to 4.1 ng/mL, 7.3 ng/mL, 8.9 ng/mL, 9.4 ng/mL, and 9.8 ng/mL every 20-40 d after the surgery. However, carbohydrate antigen 19-9 serum levels remained within normal limits after the surgery. CEA: Carcinoembryonic antigen; POD: Postoperative day; CA19-9: Carbohydrate antigen 19-9.