SMALL ENCAPSULATED HEPATOCELLULAR-CARCINOMA OF THE LIVER - PROVISIONAL ANALYSIS OF PATHOGENETIC MECHANISMS

Background. Small hepatocellular carcinomas frequently were found inci dentally during routine pathologic examinations of adult livers remove d at liver transplant. Methods. Sixty-nine carcinomas of all sizes wer e found in 25 patients; 39 of the tumors were smaller than 1 cm in dia meter, and 18 of the carcinomas in five patients were not clinically s uspected. These small incidental carcinomas lend themselves to analysi s of the morphologic basis of human hepatocellular carcinogenesis. Res ults. All of these tumors arose in cirrhotic livers. Most of the small carcinomas were multilobulated and subdivided by pre-existing fibrous septa. The surrounding capsule usually was not a true capsule. They w ere all well differentiated, most formed bile, Mallory bodies, or show ed alpha-1-antitrypsin (A1AT) positivity. Transition from cirrhotic no dular parenchyma to areas of hyperplasia or atypical hyperplasia to we ll-differentiated carcinoma were common. Large cell dysplasia also was common. Conclusions. These morphologic transitions closely parallel c hanges seen in experimental chemical carcinogenesis. They also strongl y suggest a multicentric origin of the tumors. In addition, in every i nstance, the lesions were multiple in the liver and involved both lobe s. This latter finding has possible implications for recurrence after local surgical excision of small hepatocellular carcinomas.