Early hepatocellular carcinoma with high-grade atypia in small vaguely nodular lesions

Abstract

Multistep hepatocarcinogenesis progresses from dysplastic nodules to early hepatocellular carcinoma (eHCC) and to advanced HCC. The aim of the present study was to investigate the detailed histopathological features of eHCC. We investigated 66 small vaguely nodular lesions resected from 40 patients. The degree of cellular and structural atypia and stromal invasion were assessed. The immunohistochemical expression of HCC-related markers adenylate cyclase-associated protein 2 (CAP2), heat shock protein 70 (HSP70), Bmi-1, CD34 and h-caldesmon were evaluated. Of the 66 nodules, 10 were diagnosed as low-grade dysplastic nodules (LGDN), 10 as high-grade dysplastic nodules (HGDN) and 46 as eHCC. Among the 46 eHCC, 18 nodules (39.1%) showed marked stromal invasion and/or the presence of the scirrhous component and were subclassified as high-grade eHCC (HGeHCC). The remaining 28 eHCC, which lacked these features, were subclassified as low-grade eHCC (LGeHCC) and were examined further. HGeHCC showed high levels of cellular and structural atypia and large tumor size. The immunohistochemical expression of CAP2 and the area of sinusoidal vascularization showed increases from LGDN to HGeHCC. The density of arterial tumor vessels was high in HGeHCC compared with other nodule types. Cluster analysis of these parameters subclassified 65 nodules into HGeHCC-dominant, LGeHCC and HGDN-dominant, and LGDN-dominant groups. These results indicate the increased malignant potential of HGeHCC and suggest that it is already a transitional stage to advanced HCC. We consider that our grading classification system may be valuable for considering treatment strategies for eHCC around 2 cm in diameter.

Keywords: Cyclase-associated protein 2; early hepatocellular carcinoma; high grade; scirrhous component; stromal invasion.

Figure 1

Histopathological findings of structural atypia and severe distinct invasion. A scirrhous hepatocellular carcinoma‐like pattern (scirrhous component) composed of rich fibrous stroma was seen in a case with structural atypia (a). In cases with severe distinct invasion, tumor cells showed massive portal area invasion (arrowheads) (b,c) and hepatic vein wall invasion (arrowheads) (d,e). (a,b,d) H&E stain; (c,e) elastic Van Gieson stain; scale bars = 100 μm.

Figure 2

Positive immunohistochemical expression pattern for each antibody. (a) CAP2 and (b) HSP70 showed a strong expression in the tumoral compared with the non‐tumoral liver ((b) inset) and (c) Bmi‐1‐positive regions showed clear “dot‐pattern” staining (inset). (d) Areas of CD34‐positive sinusoidal vascular architectural and (e) h‐caldesmon‐positive unpaired vessels were seen in high‐grade early hepatocellular carcinoma (HGeHCC). N, non‐tumoral liver; T, tumor. Scale bars = (a),(d),(e) 100 μm; (b,c) 50 μm.

Figure 3

Typical histopathological findings of low‐grade early hepatocellular carcinoma (LGeHCC) and high‐grade early hepatocellular carcinoma (HGeHCC). (a) LGeHCC was composed of low‐grade atypical hepatocytes with high cellularity. No severe distinct stromal invasion or scirrhous component was evident. (b) HGeHCC was composed of atypical hepatocytes with a scirrhous component. N, non‐tumoral liver; T, tumor; Sci, scirrhous component. (a,b) H&E stain; scale bars = 200 μm.

Figure 4

Proposed diagnostic flow for small vaguely nodular lesions. High‐grade early hepatocellular carcinoma (HGeHCC) is clearly diagnosed when there is a scirrhous component and/or severe distinct stromal invasion.

Figure 5

Values of histopathological factors in each type of lesion. (a) Size of nodule; the immunohistochemical expression of (b) CAP2, (c) HSP70, (d) Bmi‐1 (e) and CD34; and (f) the arterial vessel density (AVD) were compared for each type of lesion. Nodule size, CAP2 expression, CD34 expression and AVD were increased for LGeHCC and/or high‐grade early hepatocellular carcinoma (HGeHCC) compared with those of DN. CAP2 expression and AVD in HGeHCC were statistically higher than those in low‐grade early hepatocellular carcinoma (LGeHCC) (Mann–Whitney U‐test). CD34 expression and AVD in scirrhous components (HGeHCC Sci+) were significantly higher than those in the non‐scirrhous components (HGeHCC Sci−) of HGeHCC (Mann–Whitney U‐test). Circles, outlying data. *P < 0.05, **P < 0.01, ***P < 0.001; n.s., not significant.

Figure 6

Immunohistochemical findings of CAP2 and h‐caldesmon in high‐grade early hepatocellular carcinoma (HGeHCC). The strong expression of CAP2 was frequently observed in tumors showing (a) portal area invasion (arrowheads, the same area of Fig. 2b), (b) hepatic vein wall invasion (arrowheads, the same area of Fig. 2d and e) and (c) scirrhous component. (d) Areas of scirrhous component in HGeHCC were highlighted by very high levels of arterial vessel density (AVD), as indicated by the h‐caldesmon‐positive vessels. Scale bars = 100 μm.

Figure 7

Cluster analysis of pathological factors. (a) The lesions were clearly divided into three groups based on pathological factors. (b) Group I was composed of high‐grade early hepatocellular carcinoma (HGeHCC) only. Group II mainly comprised high‐grade dysplastic nodules (HGDN) and low‐grade early hepatocellular carcinoma (LGeHCC). Group III was mainly composed of low‐grade dysplastic nodules (LGDN); all LGDN were included in group III.