A case of small well-differentiated hepatocellular carcinoma with marked lymphocytic infiltrate.

We herein report a case of well-differentiated small hepatocellular carcinoma (HCC) with severe lymphocytic infiltrate (SLI) in a 55-year-old male patient with HCV-related cirrhosis. The patient had been followed-up because of HCV-related cirrhosis. He was found to have two small nodules in S8 by imaging techniques, and he underwent S8 segmentectomy. The resected liver showed two small nodules. Both were encapsulated, well-defined, solid, reddish and expansive nodules with fibrous septa. They measured 8 × 8 mm and 15 × 10 mm, respectively. Histologically, both tumours were pure HCC; the smaller showed SLI with lymphocytes/HCC cells ratio over 20, while the larger showed mild lymphocytic infiltration with lymphocytes/HCC cells ratio of 0.8. The smaller HCC was well-differentiated (trabecular thickness <3) HCC-SLI with Edmondson II = I cytologic atypia, while the larger was moderately-differentiated (trabeculae >3) HCC (Edmondson II>III>I). Extremely well-differentiated Edmondson I HCC or adenomatous hyperplasia areas were seen in the periphery of both HCCs. The patterns of SLI could be classified into the following three: sinusoids (S) type, portal tract (PT) type, lymph follicle (LF) type. In S-type, lymphocytes were infiltrated between the trabeculae. In PT-type, SLI was found to arise from extension from already inflamed PT within HCC or neighboring PT. The HCC cells frequently exhibited moth-eaten or piece meal necrosis in PT-type. In LF-type, lymphocytes were activated, and nuclear dusts were noted. It appeared that LF-type has arisen from preexisting S-type and/or PT-type. We speculated that the entry of SLI was from S in S-type, from incorporated inflamed PT in PT-type, and from both in LF-type. The approximate overall positive ratios of lymphoid cells among inflammatory cells were as follows: CD20 50%, CD3 70%, CD4 50%, CD8 30%, CD138 3%, CD163 40%, granzyme B 2%, smooth muscle actin (SMA) 30%, CD31 30%, CD21 2%, S100 3%, bcl-2 10%, CK19 1%, CD10 1%, CD30 0%, CD56 0% and Ki67 labeling index = 5%. EBV-ISH and HPV IHC were negative. Interestingly, Kupffer cells had myofibroblastic antigen in addition to macrophage antigens, and stellate cells expressed macrophage antigens aside from myofibroblastic antigens. These data suggest that, in the present case, pan-B-cells, pan-T-cells, helper T-cells, cytotoxic T-cells, plasma cells, macrophages, Kupffer cells, stellate cells, myofibroblasts, fibroblasts, endothelial cells, dendritic cells, Langerhans cells, and toxic molecules may play roles in tumour immunology.