Induction of smooth muscle cells in the fibrous capsule of human hepatocellular carcinoma but not in the septa of hepatic cirrhosis

We examined the expression of smooth muscle cytoskeleton in spindle-shaped cells in the capsule of hepatocellular carcinoma (HCC) and the septa of liv er cirrhosis (LC). Serial sections of livers resected from 11 patients were stained with monoclonal antibodies against vimentin, desmin, smooth muscle actin (1A4, HHF35, CGA7) and smooth muscle myosin heavy chain isoforms (SM 1, SM2). Capsular spindle-shaped cells exhibited a cytoskeletal feature ind icative of intermediately differentiated smooth muscle cells. Computer-assi sted morphometry revealed that the proportions of 1A4-, HHF35-, CGA7- and S M1- positive areas to vimentin-positive area were 88.0+/-11.0%, 50.8+/-17.4 %, 25.3+/-16.4% and 19.4+/-12.4% (n=11) in main rumours and 86.6+/-9.4%, 50 .9+/-18.7%, 21.1+/-12.3% and 17.6+/-9.7% (n=12) in daughter rumours, indica ting that spindle-shaped cells are heterogeneous in cytoskeletal expression . Septal spindle-shaped cells in LC lacked the cytoskeletal proteins specif ic to differentiated smooth muscle cells (CGA7, SM1, SM2 and desmin). Elect ron microscopically, capsular spindle-shaped cells contained more microfila ments and less rough endoplasmic reticulum than do septal cells. Intermedia tely differentiated smooth muscle cells are induced in the capsule of HCC b ut not in the septa of LC, suggesting a role for stromal interaction by tum our cells in the induction of smooth muscle cells.