Primary liver cancer is a rather unusual malignancy in that the incidence varies tremendously from one geographical area to another. While relatively uncom mon in Western countries, it is the most prevalent malignant neoplasm in Southeast Asia, South Africa, and many other regions; in all, the countries in which primary liver cancer is very prevalent account for more than two-thirds of the world's population. In China alone, approximately 100 000 people die every year from primary liver cancer, mostly hepatocellular carcinoma. The incidence is rising in some countries, especially Japan, where it has doubled among males in the past 15 years or so, a staggering and puzzling trend. Since the demonstration of an etiological relationship between hepatitis B virus infection and hepatocellular carcinoma, intensive research has been con ducted in an effort to elucidate the role of the virus in hepatocarcinogenesis. Though much progress has been made, a full understanding of the molecular events leading to malignant transformation of the hepatocyte will probably require many more years of rigorous investigation. Chemical carcinogens and several industrial pollutants may also be involved in the etiopathogenesis of neoplastic liver disease."

This is a classification of tumours and tumour-like lesions of the liver. It is based primarily on the microscopic characteristics of the tumours, and is therefore concerned with morphologically identi- fiable cell types and histological patterns. The haematoxylin- and eosin-stained section remains the mainstay of morphological diag- nosis, but special histochemical stains are often helpful and have been referred to in the explanatory notes. Readers interested in specific special stains mentioned in the text should consult Labora- tory Methods in Histotechnology of the Armed Forces Institute of *Pathology, Washington, D. c., USA. 1 The results of immunohisto- chemical methods for identifying various tumour "markers" have also been noted whenever indicated. The present classification incorporates all the previously classi- fied tumours, but also includes several new lesions, viz. biliary papil- lomatosis, the fibrolamellar variant of hepatocellular carcinoma and epithelioid haemangioendothelioma. Several subtypes of hepato- blastoma are mentioned. A serous type of bile duct cystadenoma is described. The section on tumour-like lesions has been expanded to include focal fatty change and inflammatory pseudotumour. The section on adenomatous hyperplasia, including macroregenerative nodules, has been amplified. The number of photomicrographs has been increased from the original 56 to 150. Unlike the first edition, the photomicrographs in the second edition are mostly black and white. All are new and were taken of representative cases on file at the Armed Forces Institute of Pathology.