Keratin 19 marks poor differentiation and a more aggressive behaviour in canine and human hepatocellular tumours

Abstract

Background: The expression of Keratin 19 (K19) was reported in a subset of hepatocellular carcinomas (HCCs). K19 positive HCCs are associated with an increased malignancy compared to K19 negative HCCs. No suitable mouse models exist for this subtype of HCC, nor is the incidence of K19 expression in hepatocellular neoplasia in model animals known. Therefore, we compared the occurrence and tumour behaviour of K19 positive hepatocellular neoplasias in dog and man.

Results: The expression of hepatocellular differentiation (HepPar-1), biliary/progenitor cell (K7, K19), and malignancy (glypican-3) markers was semi-quantitatively assessed by immunohistochemistry. The histological grade of tumour differentiation was determined according to a modified classification of Edmondson and Steiner; the staging included intrahepatic, lymph node or distant metastases. Four of the 34 canine hepatocellular neoplasias showed K19 positivity (12%), of which two co-expressed K7. K19 positive tumours did not express HepPar-1, despite the histological evidence of a hepatocellular origin. Like in human HCC, all K19 positive hepatocellular neoplasias were glypican-3 positive and histologically poorly differentiated and revealed intra- or extrahepatic metastases whereas K19 negative hepatocellular neoplasias did not.

Conclusions: K19 positive hepatocellular neoplasias are highly comparable to man and occur in 12% of canine hepatocellular tumours and are associated with a poorly differentiated histology and aggressive tumour behaviour.

Figure 1

Examples of canine nodular hyperplasia. Immunohistochemical staining of K19 negative cells is shown in (A). HE staining, double layered cords of well differentiated hepatocytes are shown in (B). Absence of immunohistochemical staining for glypican-3 is shown in (C). Positive immunohistochemical staining for HepPar-1 is shown in (D).

Figure 2

Examples of canine K19 negative hepatocellular tumours. Immunohistochemical staining of K19 with a negative tumour field (left) and positive reactive ductular proliferation at the periphery of the tumour (arrow) is shown in (A). HE staining, trabeculae of well-differentiated hepatocytes with a uniform appearance are shown in (B). Absence of immunohistochemical staining for Glypican-3 is shown in (C). Positive immunohistochemical staining for HepPar-1 is shown in (D).

Figure 3

Examples of canine hepatocellular tumours with high K19 expression. Immunohistochemical staining of K19 positive cells is shown in (A). HE staining, trabeculae of hepatocytes with cell pleomorphism and multiple mitotic figures (arrowheads) are shown in (B). Immunohistochemical staining of glypican-3 positive cells is shown in (C). Immunohistochemical staining for HepPar-1 with tumour negative area and positive area of surrounding non-neoplastic liver (arrow) is shown in (D).

Figure 4

Examples of K19 negative human hepatocellular tumours. Immunohistochemical staining of K19 negative cells is shown in (A), positive bile-ducts at the periphery of the tumour indicated by arrow. HE staining, moderately differentiated hepatocytes with trabecular growth pattern is shown in (B), absence of immunohistochemical staining for Glypican-3 is shown in (C). Positive immunohistochemical staining for HepPar-1 is shown in (E).

Figure 5

Examples of K19 positive human hepatocellular tumours. Immunohistochemical staining of K19 positive cells is shown in (A). HE staining, poorly differentiated HCC with a diffuse growth pattern and multiple mitotic figures (arrowheads) is shown in (B). Immunohistochemical staining for glypican-3 positive cells is shown in (C). Absence of immunohistochemical staining for HepPar-1 is shown in (D).